I didn't actually get any submissions for my FF1 balance contest. This didn't hugely shock me as it isn't like everyone goes through a 'must play random old video game X' phase at the same time. That said there were some interesting discussions in the comments so I figured I would post what I came up with anyway.
1. Intelligence does something! Intelligence adds to your chance to hit with spells. This makes the Black Mage significantly better at casting attack spells than Red Mage / Ninja and that all that Int the Black Mage gets is useful. Base success rate of spells reduced from 148 to 128 for players so that overall spell damage does not inflate too much.
2. Many bad single target spells now hit all applicable targets. I would have included Rub in this list but since several mobs cast it on the party and it is already brutal when they do this I don't think changing Rub is a good idea. It means Rub is still bad for players to cast and devastating when used against them.
Fire, Lock, Lit
Sabr, Blnd, Brak
3. Several bad spells doubled in efficacy. As part of this all buff/debuff spells no longer stack. Specifically the dodge spells need to not stack so that ridiculous situations like the whole party being invulnerable to physical attacks don't occur. I realize this makes the White Mage only party totally useless but I am okay with that.
4. Changes in spell levels: Pure to L2, Soft to L4, Mute to L6.
The idea behind these changes accomplish 2 things. First, to make spells that were almost never worth casting actually decent, which is true for most of the changes. The other major shift is to make the low level BMagic damage spells decent. Low level BMages are total junk compared to melee because they get only a couple of decent actions before they are back to swinging uselessly with daggers. Now BMages will actually have a few totally awesome actions before having to resort to useless swinging instead! RMages might even learn and cast attack spells before Fir2 also. Obviously beyond about level 10 this stops being very relevant, which is fine, because at that point BMages have enough spells they can contribute pretty consistently.
Thief and Fighter changes.
Mostly people agree that all the classes have good and bad points and are reasonable inclusions in a party except for Fighter and Thief. Fighters are flat out the best to the point that it is probably almost as quick to win with 2 Fighters as it is with a 4 person party including 0 Fighters. Thieves are unbelievable junk. The primary reason for this is Fighters get the best attack progression, best weapons, best armor, best HP and best damage progression and Thieves get to be either average or terrible at pretty much all of these. Changes:
Base Attack%: 5 (was 10)
Attack%/level: 1 (was 3)
Base Attack%: 10 (was 5)
Attack%/level: 6 (was 2)
With these changes Thieves hit about as hard as Fighters used to and Fighters hit about as hard as Thieves used to. Fighters will still be massively tough and fantastic for filling the front line but for hard hitting physical attacks you will want either a Thief or BB.
These last changes are designed to make the parts of the game that were simply too easy significantly more challenging. I don't mind some parts being easier than others but in any fantasy setting the final boss is supposed to be a real challenge and the fight should take awhile. Many of the game's dungeon bosses are simply too weak and die too quickly - it is common for a fairly challenging dungeon to be ended by a boss fight that lasts only 1 or 2 combat rounds.
Vampire, Lich, Kary, Kraken, Tiamat, Chaos: Health increased by 100%.
Pirates: Health increased by 900% to 60.