Here are a few limit break ideas for you.
Allow Break Arts to be taken for 2 or 3 points, but the art chosen is random, like this:
Taking Neutralize twice removes immunities and resistances in addition to the normal effects.
Notes on limit break abilities:
You probably shouldn't be able to take Attack (Physical) and Attack (Magical) with the same limit break...or the cost of the second attack should double, then, which is the same as Multi-Attack's cost of 6 points. Choosing Multi-Attack along with both should only give one extra attack, chosen between physical and magical.
Question: Looking through the status effect section, combining mini and poison would increase the damage poison does each round to 15% (from 10%), since it doesn't specify what types of damage are increased (in other words, it says all damage is increased). Is that intentional?