I was a little bored, and seeing as how Law of the West isn't really worthwhile for me to hack at the present (see below), I figured I'd give my subjective opinions on how hard the games in 1987 would be to hack based on a cursory look at them.
The Black Bass (J): Probably wouldn't be too hard. Doesn't look like much text, and there's a good amount of free space in the fixed bank for routines. Helps that this is the kind of game where a terse translation would work. The pointer table is unusual (six bytes per entry, first byte is text length, second byte is number of lines, next two bytes are PPU address, last two bytes are the pointer) but I don't think it'd be very hard to make a dumper and inserter for it.
Law of the West: This one uses a nasty pointer table format that looks like this:
01 01 00 02 02 0A 0A 00 03 03 0B 0B 00 04 04 0C 0C 00 05 05 0D 0D
Where the zeroes are padding bytes, the low numbers represent pointers for the question asked of your character followed by four possible responses, and the high numbers represent pointers for the next set of pointers based on which of the responses you chose. Not a whole lot of free space to make use of either. Since this game is already available on other systems, I don't really have the inclination to deal with this.
City Adventure Touch: Mystery of Triangle: Looks simple. Bog-standard pointer tables and plenty of free space in the fixed bank. The small text window is a big pain in the butt, though. The biggest challenge in this hack would probably either be making the window bigger (there's a lot of space for that) or dealing with it.
Sanma no Meitantei: Normal pointer table, but since this is a Portopia-style adventure game there's a good amount of text. Not much free space in the fixed bank. Lots of free space elsewhere, but hard to tell how much good it would do. Would probably require playing with bankswitching and/or expansion to do this one.
Morita Shogi: Didn't look closely at this one. Most of the text is in small icons so the difficulty in the hack would probably lie mostly in pixelart skills.
Takahashi Meijin no Bug-tte Honey: I beat this game a long time ago because the amount of Japanese text in it was miniscule. Based on that, I'm guessing this would be the easiest hack on the list, maybe just a title-screen hack.
Hokkaido Rensa Satsujin: Okhotsk ni Kiyu: Judging by the text routine and a look at the ROM, this Portopia-style game crams all of its text into a 64K area of four banks with a massive pointer table at the beginning. No free space in either those banks or the fixed banks. Surely impossible to do without expansion, which would probably necessitate a nasty hack of the text routine and pointer tables to allow for more than four text banks.
Tokoro-san no Mamoru mo Semeru mo: This uses a truly bizarre text routine where it first reads the necessary information from a certain CHR bank using the PPU_DATA register. This information is encrypted by being jumbled up in a certain way, so after this it has to run it through a decryption routine. The first routine is at $8112 and the second at $8084. Why the hell they went through the trouble of encryption for such an obvious kusoge, I couldn't say. On the bright side, once you figure out the encryption the hack would be very simple, since the text routine prints to the entire screen. Assuming that all of the Japanese text in the game is like this, it looks like only four screens at most would need to be translated.
Jongbou: Like the shogi game, I didn't look closely at this one. But there's a ton of free space in most of the banks and a decent amount in the fixed bank. The game already has an 8x8 text routine to replace the 16x16 with as well. Probably would be pretty easy overall.
Family Trainer 5: Meiro Daisakusen: This uses a standard text routine and pointer tables and there's a lot of space in most of the banks, though little in the fixed bank and none in the bank before it. This may not be a problem, though, since the intro text at least is in the first bank. Even if there is text in the banks I mentioned, two of the other banks are completely empty, so moving the text to one of those would probably be relatively easy. The biggest obvious problem is the small text window during gameplay, but there you'll still have double the lines to work with since the Japanese text has to waste half the lines on dakuten.
Family Mahjong: Again I didn't look too closely. There's a decent amount of free space in all of the banks except the fixed one, but you could probably squeeze a respectable DTE in the latter if necessary. This game also has an 8x8 routine to replace the 16x16 routine. As usual with these traditional mahjong games, the biggest difficulty would probably be screen space during the gameplay segments.
Tenka no Goikenban: Mito Koumon: Aside from the obvious problem of the really impressive spoken dialogue at the title screen, this game also has very little free space and none in the fixed bank. Furthermore, it's not expandable in its current state and uses a proprietary mapper that has no obvious analogue (to me, anyway) to other mappers. I didn't bother looking any further than that.
Tsuppari Oozumou: Yecch, vertical text. Aside from that, it's got 16x16 text including a name entry screen, and only one strip of 256 bytes of (I'm assuming) unused empty space. Whether or not this would be enough to hold the code necessary to change the mapper to 41 (something which I would suggest for Space Hunter, incidentally) as well as any other necessary hacks that there isn't enough space in the existing code for is hard for me to say, whether or not you went through the herculean effort of converting it to horizontal text.
Zoids: Chuuou Tairiku no Tatakai: An RPG, with the attendant large script. No obvious free space in the fixed bank, which isn't conducive to major hacking work. However, the ROM is expandable and it shouldn't be overly difficult to come up with methods to get at that extra space without major rewrites to the text routine if you can find somewhere to put the minimum necessary code. There's also a decent amount of text already in English (mostly the Zoid names).
SWAT: Special Weapons and Tactics: Much like Zoids, an RPG without much free space that is well within the realm of possibility to expand if one can cram the code in somewhere. It also has the reputation of being a very hard and buggy kusoge, so have fun with that.
Ide Yosuke Meijin no Jissen Mahjong: Yet Another Mahjong Game that's like all of the other ones except that it uses a special controller. Shouldn't cause any hacking problems, but will take getting used to. Again, no free space in the fixed bank, though there's a good amount to be found elsewhere.
Kyonshis 2: Like Mito Koumon, this is a 256KB game that uses a proprietary mapper. However, this is a more complex mapper and in theory the ROM is expandable, though I see no documentation to confirm this and don't know what if any emulators support it. Some banks have some free space, while the others including the fixed bank are more stingy. This game uses three variable 8KB PRG banks, which may be helpful. Also, the text is encoded strangely (some tile values have $#80 subtracted from them, others $#86), which is a minor annoyance. Lastly, there are a lot of control codes and they're embedded in the pointer table instead of the text, a much greater annoyance.
Indra no Hikari: Tired of RPGs yet? This is an MMC1 game and thus very expandable, and due to the fact that there's a PRG access mode that unfixes the fixed bank, you can probably exploit this relatively easily (though I admit I have no experience in this area). There appears to be a small strip of free space at the end of the fixed bank to facilitate this. Combined with the standard pointer table, this might be the easiest of the RPGs to do so far, though still a large task obviously.
Hoshi wo Miru Hito: Perhaps the last true "densetsu no kusoge" on the Famicom yet to be fully translated (definitely the most well-known one), Stargazers has the big advantage of having a lot of work already done. Since KingMike is the one who did it, he'd be a better source for information about it than me.
Uchuusen: Cosmo Carrier: While this game uses standard pointer tables, the text and pointers are scattered all around, at least for the main interface. Furthermore, the code for the text routine is in the non-fixed banks, which is a pain but could possibly make expansion easier. Unfortunately, it uses a proprietary mapper with single-screen mirroring that isn't expandable. The closest analogue appears to be MMC1, but it would still require some work to convert mainly due to that mapper's unique method of bankswitching. On the bright side, there's free space in the fixed bank to facilitate that, as well as some free space elsewhere. The text routine also requires an extra byte to print dakuten, which would allow for some savings.
Artelius: The only real problem with this one that I saw is the lack of free space in the fixed bank. It's an expandable MMC1 game with a standard text routine and quite a bit of free space in some of the other banks. The text code is again in the non-fixed banks, which may make the full fixed bank less of a problem. Best of all, a lot of it is already "translated" into Engrish.
Outlanders: This is an expandable UNROM that uses a standard text routine, but there's not much free space anywhere. Not much else to say about it other than the fact that it's a clunky action-RPG with the requisite amount of text.
Yamamura Misa Suspense: Kyoto Ryuu no Tera Satsujin Jiken: This uses the same mapper as Kyonshis 2, but there's basically no obvious free space anywhere. On the other hand, while the text routine is normal, a profound amount of space is wasted both on dakuten and padding spaces for the beginning of lines. The reason for the padding spaces is so dialogue will appear indented after the name of whomever is speaking. It probably wouldn't be difficult to write a control code to add this padding or just remove it altogether, though that might still not solve your space problem.
Ginga no Sannin: Arguably the most-wanted translation on this list. I believe KingMike said he planned to come back to this one this year. It's another UNROM without much free space to work with. It uses a standard text routine with the strange twist of it having to read what seems to be junk data before it starts copying text to RAM. Control codes are also handled in a separate step, and the game already appears to use its own dictionary compression routine.
Mesaze Pachi Pro: Pachio-kun: Another MMC1 game with free space here and there, though not much in the fixed bank. Looks very straightforward otherwise.
Pro Yakyuu Famista '87: This is just the original Famista (RBI Baseball) with new league data. The biggest difference is the addition of two teams, which unfortunately makes this not quite as simple as hacking RBI Baseball like the diehards do with Tecmo Super Bowl every year.
I would be willing to try my hand at hacking some of these if someone else would translate the scripts.
