Also, "balance is not important in SP game" kind of reasoning is absolutely incorrect.
For turn-based games, good balance is EXACTLY what sets good games (i.e. XCOM 1/2) from bad games (gazillion of XCOM clones).
The individual tweaks to skills altering cooldown, stat bonuses, etc are fine. This is an overhaul of basic game mechanics that makes it more difficult for any character to use psi. Pure builds suffer from being restricted to a whopping 6 skills max and greatly increased psi cost and hybrid builds that don't invest much in INT will only get 2 on top of everything else and thus not much reason to invest in psi. This can all be fixed with two things.
1. Increase the slots for available spells with the MINIMUM being six.
2. Remove the increased psi cost for having spells from different schools.
There's a few minor tweaks I'd make like how force field should have reduced health but it doesn't dissipate if one column is destroyed but those two points need to be implemented otherwise a lot of potential builds end up in the trash. And I can't believe I have to say this: If you don't like pure psi THEN DON'T FUCKING PLAY PURE PSI. Again, you are NOT FORCED to play one specific way. Pick one of the dozens of other builds that you enjoy and let people have fun being a meth huffing cave wizard.