Let's discuss Iris Havengard

Anyway, Lockirby2, let's run with the idea of M.Sword. What if it checked Iris's level (X), doubled it, and used that as a probability out of 255 for casting a spell of that element [2x/255]. Examples (pulled randomly from memory):
Fire = Flame Skean
Bolt = Bolt Edge
Ice = Blizzard
Water = Water Edge
Wind = Wind Slash
Earth = Surge
Poison = ???
Holy = ???

So if Iris were at level 30, and she chose Fire, she would do a fire attack, and then have a 2(30)/255 (24%) chance of also casting Fire Skean. At level 60, she would have a 47% chance of casting the spell. Too complicated?

With spells similar in power to Fire Skean, Bolt Edge, and Water Edge, I think this works fairly well because she'll get good damage from the spell in the early-game and it will hopefully transition to good damage from the elemental attack in the late-game (she'd pretty much be married to Edgar with his Debilitator if she wants to use the skill against the statues or the final boss though).  Still doesn't beat Ultima spam in most situations, but pretty much nothing else does either, so maybe that isn't a fair expectation.

I'd say just to make the chance of proccing a flat 50% assuming the spells that you listed above.  It has to be able to compete with simply casting Fira/Blizzara/Thundara from the back row, and it doesn't do that IMO unless it hits significantly harder on average (2x as hard with a good setup like using a Genji Glove for two proc chances is ideal IMO).  If she uses it from the back, her damage will presumably be cut in half like it is for weapon procs, and this makes it even more pointless.  A 10-15% chance of casting something in the WoB doesn't cut it.  Tying the proc chance to level makes the spell procs less useful in the early-game, which is exactly where this skill needs the boost the most, so I think it's not an improvement.

I also think that we would need to keep the ATB full after setting up the M.Sword (similarly to Morph) for it to be usable in random encounters (or even most boss fights given how short they tend to be).

Personally, I could understand building this off of vanilla or the bugfix compilation (I'd probably prefer the bugfix version, but I don't really care).  Adding Iris on top of Divergent Paths feels kinds weird IMO.