ff 3/6 thoughts

I hate Steal.  You've got to use a relic slot to make it have any reasonable chance to work, and another to do damage that turn.  It's a complete waste.
I've seen a lot of people recommend that mods replace it with Capture outright, but I've got a different approach I'm going to try: putting the Thief's Knife ability on ALL daggers, restricting them to Locke, and then giving him X-Attack as a special (with an ASM patch by Madsiur to make it randomly strike 2-4 times). EDIT: Scratch that, I thought X-Attack was a separate battle command that could be set in another slot.  It's relic controlled, and I haven't figured out how to simulate relic effects on stuff other than equipment yet.  So I guess the Capture swap really is the best option.

As mentioned earlier, Haste2 and Slow2 are a waste of spell slots.  Letting Haste and Slow multi-target for double MP cost (like every other spell) is a much better option, and frees up some spell space.  Same goes for Protect and Shell, and possibly Antidote.
...Speaking of which, Antidote needs to remove more status ailments or Poison needs to be much more dangerous. There's a patch that makes it and Seize calculate based on max HP, though, which would make Antidote more important.

Not a fan of Slot.  People have tried to fix it, but it's either too weak or too strong.

Merton's pretty bad.  I've got an idea to make it more interesting, which you can try if you like:
>Inflicts 16/16ths of target's HP, killing everything on screen that has less than 9999 HP (including your party).  Non-elemental, cannot be dodged.
>Casts Life3 on every target hit.
Basically, it does huge damage to boss enemies, but they'll raise with 1/16th their HP after you beat them if you've cast the spell this fight.  Likewise, it puts your entire party into critical.  More effective with a damage cap lift.

X-Zone is the worst spell, though.  Not because it's useless, but because it's TOO useful.  There's no reason to ever bother learning or using Doom.