I know I already complained about SF2, but more specifically, I think a hack that redid the format of the game and tweaked its plot a LITTLE could be a really amazing game. Specific ideas (There are light spoilers ahead, FYI!):
--Plot is no longer told over a "generations" mechanic (which really, in retrospect, seems like it was forced). Players choose 1 of 3-4 characters (I think Gustaf, Ginny, and maybe one of the generic diggers or other nobility), and all usable characters would be available to recruit during the course of the game. Gameplay takes place during 1 time period, the final one.
--This isn't to say that the historical stories told wouldn't be a part of things, as I think using most of the historical plot in SF2 for Lore and background would be a better use of the better parts. I think there's more than enough to use creatively here--I'd just like more of a focus on the era where most of the interesting stuff happens rather than the leadup, which tends to be pretty dull plot-wise.
--Since most of the SF2 cast has literally zero background other than as super generic archetypes, I feel like the hardest part of this would be writing in side stories that maybe gives you the excuse to recruit these people rather than just "I need more people in my party". IMO there's a decent amount of lore to work with, and a relatively talented writer could probably make up some decent side-stories. And dear god how hard would it be to give townspeople more than 1 line (the same line for ~70 years no less!)?
--Give access to areas in a traditionally SaGa way: once you unlock a locale, it becomes available to visit whenever (unless plot-specific things happen, like the mine cave-in). I feel like this is the best way to take care of the "getting locked out of stuff" problem that plagues this game, especially regarding town services access.
--I think the plot towards the tale end (with The Egg, Edelritters, etc) could stay generally unchanged with more opportunities for enhancement: I mean, other than the 1 Edelritter that actually gets face-time, who are the other 5, exactly? I personally think there are a lot of chances for some very good reworkings here that definitely were not taken advantage of in the slightest.
The biggest problem (outside of actually hacking this game) would be the available materials in-game. For a SaGa game, there seem to be surprisingly few locales and even those are relatively small! This might have just been my perception being off, but I think to make this work, you might need to expand some dungeons or even manufacture entirely new ones--and with the unique art-style of this game, I'm not sure if that's doable. But reusing certain dungeons that literally are only seen once in the original could probably work too. (if anyone knows about any unused resources on the disc, I'd definitely be interested to hear about it!)
Even if you don't change some of the game systems (which IMO have a huge amount of extra nonsense that could be consolidated too, especially regarding enemies), I think these admittedly large changes could really fix some of the biggest problems this game has while still maintaining what makes it good.