Most of the equipment is going to be rebalanced anyway, so I'm not worried that class abilities will unbalance things. I'd like the middle game (Castle of Ordeals and Ice Cave) to be less "difficult" and more "challenging", the endgame to be less easy and more interesting, and the beginning to have much less grinding, especially at Elfland. I like a lot of what Square did in the FF1/2 remake for GBA (though they messed up a few things too).
You mean less insane/imbalanced (Sorcerors), but more appropriately challenging. The FF1 remake made the game significantly more easy than the already buggy FF1.
One thing I want to do away with is number limitations. You can have more than 9999 HP or 999 MP and you can do more than 9999 damage. The sky's the limit. Somewhat related to this is how I want to handle weaknesses and resistances, but more on that later. I've gotta go.
Well, there's always the classic algo in multipliers or FF1 extra damage (although, that method is borked for the most part until the Advance version AFAIK, and unfortunately doesn't scale IIRC).
So with resistance, weakness, absorb, etc., I wanted to use a sliding scale similar to what FF8 did with its junctioning system (don't worry, no GFs and no drawing in my engine). Basically, equipment effects can be cumulative. You start with a value of 100 for each element, meaning that you take 100% damage (normal) from that element. If a piece of armor provides 50% resistance to fire, your fire value is now 50, so you take half damage. If you wear several pieces of armor that provide resistance, the value keeps decreasing until it goes negative, and then you absorb fire damage. This opens up the door to all kinds of neat equipment effects, and combining them creatively in your party. I really liked the mechanics of this system in FF8, but the whole magic draw and junctioning stuff, and the total lack of equipment made it completely uninteresting.
I wish I got to play FF8 on PC (then again, that would require its own miracle).

Cumulative equipment could work I guess.. it seems Diablo-like, minus the cap.