This is really bad changes and it fixes nothing. If psi builds will be forced to specialize in one tree that means even more excess skill points and more cheaper build to spec in overall.
What psi does have an issues is lack of sustainability in any of the school, lack of spells, and high expense of those.
4 Branches (1 is support) so it cannot be counted as an actual damage branch.
So 3 branches. None of them are sustainable to walk you through the game. You can do it with knives, you can do it with sword, you can do it any gun selection, but you cannot go through the game with just 1 psi branch.
I was going metathermics and telekinesis before last boss, where I had to switch to thought control to kill him. Because metathermics maxed out would deal no damage to Tchort, unlike though control that ripped him apart in 1 turn.
Thought Control absolutely useless vs robots and if you go it I cannot see you getting through GMS compound. Even if you go telekinetics, Electrokinesis is a very weak and highly expensive spell vs robots, and metathermics is useless.
Psi builds are extremely slow due to "spell cooldowns" and the need to regenerate psi points, the 100 you have is like 2 spells or 1 turn at best. Note as well as due to low agi low dex, low str. Any psi build is lacking = Good metal armor, Good initative, Good movement speed, Good dodge and evasion. So you are literally a glass canon that always moves second, you also already have minus -20-25% hp vs any other game class.
Overall changes would not be that bad if you would fix each branch of psi making it more variable and sustainable and add proper weapons to psi build, cuz running whole game without weapon, and just later crafting 1 vest and 1 headband is beyond lame.
Yes when you had access to all 4 branches, there was a lot of utility and crowd control. But this limits don't solve any of the issues of the psi and I would not say PSI was OP in the first place.
Making a knife build allowed me to clear the game like twice faster never have issues with any robots, or running out of psi.
Like seriously can anyone please try to start a new game and spec into psi build chose your school and play it through? Doubt you will even clear first mission with rathounds.
The first spell learned - TK Punch costs 50% psi, does LOW damage and has 3 turn cooldown. So you will have to use guns instead of psi....
So overall.
Psi builds were weaker than any knife / weapon build before update and cleared game slower, now its not even worth starting a game with a psi build, good luck specializing in one tree and getting through whole game.
Seriously a much better change would be to add psi weapons, wands or whatever, and make them chargeable with batteries or something like that. They would amplify one particular branch of psi abilities and cost certain energy per each spell casted.
Also add +6 spells to each branch or rework existing ones to allow different types of damage. Does not make sense to spec into psi build that only damages humanoids.