Great idea!
you can add 'Static States' to your Materia right now by using the standard RPG Maker 'Traits' box in the database (which will apply the state the moment the Materia is equipped), it is not currently tied to the leveling/AP progression.
But i will add a 'State Progression' feature in the next update that will allow you to tie specific States to AP thresholds, just like Skills!
Update is coming today/tomorrow :)