The rank system could definitely be expanded upon. Currently it only makes gaining weapon/spell/evasion/magic resist experience easier, but it could be worked in to other calculations or applied in different ways. Something like only allowing experience gain if skill level <= round(rank * 2.25) might match up with one of your earlier ideas. Did you have anything else in mind?
At the moment both patches are theoretically language-independent, which I see as a benefit; a language-specific patch would be free to add some new strings for things like evasion/magic resist level ups and displaying additional info in the status menu.
The menu scrolling bug was probably the most seriously broken logic of any of this project's fixes. The game keeps a pointer to the read indices into the string describing the list for the start and end of the currently displayed portion. Scrolling forward takes the pointer to the end position and parses forward one line, and scrolling backward takes the pointer to the start position and tries to parse backward one line. However, the encoding for the list strings does not use fixed-length tokens, and the code for backwards parsing of variable-length tokens is fundamentally flawed, incorrectly assuming that every multi-byte control code is preceded by another multi-byte control code. It quickly loses alignment with the string and starts interpreting control code parameters as control codes, continuing to parse too far backwards until it reaches a $0F control code parameter (which it misinterprets as a control code) followed by a line control code, and that's the string position it uses for displaying the updated scroll list.
I recently completed a solo pure mage run of the original game, and it wasn't as bad as I thought it would be. The rules for this game were that it had to be a solo run (i.e. only the same 1 character could participate in battle, other than the first battle they were present in where killing them off was my highest priority) and it had to be a pure mage run (i.e. the character could only use magic/magical items, never physically attack). I decided to use Maria due to her stats, particularly her Agility; evasion is hugely important in this game, and since she wouldn't be attacking she wouldn't be gaining weapon skills, so she wouldn't be getting any decent multipliers on weapon evasion rates, so her evasion % would be low, leading to fewer Agility stat gains and consequently lower natural evasion %. After selling unwanted equipment, I equipped her with a pair of starting shields for the evasion boost (taking a 140 spell penalty, but the early game spell bonus isn't that great anyway) and then, knowing that turtles would be my first obstacle, bought her Blizzard.
After some light grinding for HP/MP she was ready to set out for Fynn, and the adventure proceeded smoothly up to Semitt Falls, where I had to stop to build up my max MP in order to make it through the cave with enough MP to spare for the bosses (Blizzard at level 2 was quite sufficient here) and the trek back to town. After that, more smooth sailing up to Kashuan Keep, where the first real challenge for a mage awaited: Red Souls absorb all elemental magic, which meant I needed some damage-dealing non-elemental magic, i.e. Drain, Flare, Holy, or Ultima. The only option available at this point in the game is Holy, so I had to scrounge up 20000 gil and make my way to Mysidia. Grinding around the Dreadnought landing area was profitable in several ways and scored me a Mage Staff, source of free Thunder 5 spells. Since Maria had been the only valid target for basically each and every monster attack throughout the entire game, her evasion level was proportionately higher than normal, so even with a relatively low evasion % she was difficult for most monsters to hit physically by this point, and her HP growth had stagnated; weathering magical attacks from Ogre Mages brought some welcome boosts to Stamina and max HP.
After sneaking my way into and out of Mysidia via exploiting save/heal to avoid encounters (had I been more ambitious, the treasures from Mysidia Cave B1 would have been fantastic to grab, but I decided against the attempt), I brought Holy up to level 2 while walking back to Kashuan Keep, and with that Mage Staff to take care of inescapable random encounters, I made it to Red Soul in pretty decent shape and Holy slowly but surely took it down.
For extra fun I decided to fight my way through the Captain guarding the entrance to the Dreadnought; Maria's evasion wasn't high enough to make that entirely safe yet and her HP was still low enough that a lucky crit meant serious trouble, so I decided to employ the Blink strategy for this fight. It took a few resets, but eventually I was able to stack enough Blinks to survive; after heading back to town to restore my depleted MP, the next few segments of the game went by without much difficulty.
The Queen Lamia scene was slightly amusing with Maria as my party avatar, and a little bit scary for being the first monster in a while that was able to penetrate Maria's evasion (which was up to 9-70 at this point). Charm 9 was more dangerous to my meta-game of having 0 physical attacks than it was to Maria's chance of survival, but fortunately the Deist cave provided me with a Wall-16 item, so I put that to good use and lucked out with a Ribbon drop, solving my future worries about Confusion. There were no serious challenges from there to the Pandaemonium bosses, and along the way Maria's Agility finally got high enough that I could ditch her two shields for a Defender/Main Gauche combo (55 spell penalty, the first time I actually got any spell bonus) and then just a Main Gauche (5 spell penalty, yay!).
Unfortunately, monsters had enough HP by this point that most of them took several rounds to kill even with 90 Intelligence and a low spell penalty. Battles become rather tedious when you can only deal < 800 damage per turn against normal monsters and < 200 damage per turn against magic resistant monsters; finding an enemy with an elemental weakness is very nice. Once she gained Osmose, Maria became very self-sufficient, but her high evasion had left her with low max HP (< 1000 by the time I reached the first Pandaemonium boss), which meant she was in danger from bosses with strong magic attacks such as Flare 16. Fortunately for me, Osmose is highly effective against monsters, and even at level 3, 2-3 castings of Osmose was enough to defang the Pandaemonium bosses, and without their magic, it was virtually impossible for them to break through Maria's evasion. Maria reached the Emperor with a grand total of 1082 HP, 676 MP, 12 STR (I was consistently lucky with not losing STR on SPR gains), 83 AGI, 36 STA, 94 INT, 52 SPR, 35 MAG, 16-90 EVA (I'm pretty sure this would have been more like 20-90 uncapped), 9-97 MGR, Blizzard/Fire at level 9, Thunder/Scourge/Holy at level 8, Flare at level 5 (it's acquired so late in the game...), and 1-00 in all weapon skills!