Roll the immobilize from subdue into mental blast, give a new blast with some exotic damage type (brain freeze with ice or brain storm with electricity)
Increase tk blast to high damage
Increase speed of ticks of tornado, change to psi/cold
Increase damage of psychic scream, add -resist
maybe add something aside from -recharge to the set as a whole - like for example “Thought Seize: inflicting a status effects causes your next attack to lower the targets recharge and increase your own” or something like that.
really though psi just needs a damage boost, some animation clean up, and probably a little endurance relief, it definitely feels better on a blaster than a defender/cor despite originating there