Why I think this:
Every class in the game can in some way use weapons (That fit their role) in ways unique to them. Ogrin has an entire arsenal of unique weapons; Zealot can passively/actively speed up their swings as well as add a lot of damage depending on health and Vet gets a zoom for his ranged weapons plus an increase in damage. Psyker at max charges gives you a damage increase to non force weapons. A +damage buff feels to me like its not enough to differentiate the use of weapons from other classes especially as a trade for not having access to heavy hitters like bolters, braced auto-guns or the shotgun. Even if we overlook this a full non force Psyker can’t use certain perks as effectively (Warp absorption, warp unleashed) and both their main and side weapon don’t in any way interact with their kit beyond a passable buff.
What I think could solve this:
In my opinion Psyker should be able to burn warp charges and peril to uniquely interact with their weapons in some way, trading momentum for power. For the purpose of explaining this I will try to create 3 proof of concept interactions for the main 3 styles of Psyker (Melee, gun, staff)
Melee:
Melee would be one of the easier ones, giving Psyker the ability to temporarily infuse their weapon with one of their charges and some peril to a similar effect that Vet gets with their force sword. This would make melee psyker a lot more dangerous, for a very short burst of time and given the right conditions. Essentially this gives Psyker the ability to clear hordes in melee while his peril and charges are still on but the moment they run out if he is out of position then ascendant blaze is not going to save them.
Zealot and Ogrin still get to shine as the main frontliners but push comes to shove Psyker can temporarily back them up with some force moves but will need to take a breather to quell and reload their warp charges after they are done.
Gun:
Gun psyker I think shouldn’t increase their damage (That’s Vets thing and I wouldn’t want to step on their class), instead giving them the ability to reload their weapon with “warp bullets” by burning warp charges and adding some peril would probably give them their own niche. Vet relies on precision and having the biggest gun to deal with elites easily, while Psyker could shoot at hoards/shooters while not draining resources from more ammo intensive weapons (Bolters, plasma, shotguns…).
Vet still gets to be the big gun, big headshot class but Psyker is allowed to exceed in sustained long range damage as well as offer a different experience to people who dislike ammo conservation and want to dakka in peace while getting some use from force attack perks. This could be balanced around certain %ammo reload per warp charge spent or just left at max depending on the results of testing.
Staff:
So as to not leave staffs in the dust this should probably also allow staff Psykers a new way to use them. Giving staffs a burst option would probably make the most sense to differentiate them from the gun option, especially since they don’t use ammo regardless. Burning a warp charge to skip the charge time (and maybe peril cost) of a charged hit would make staffs into fantastic burst tools.
Staff Psyker becomes a lot more about knowing when to crack into your reserves of power as the situation demands it. It exchanges charging the weapon now for having to charge a BB later as well as dropping your damage overall for more DPS now. This could give Psyker some clutch potential as they cut loose.
Small minor points:
How would you trigger this? Hold alt fire I think would fit, given that this change still needs to fit within a controller.
Ascendant blaze and Quicken should probably not take away charges but instead just take into account the fact you have them.
Overall conclusion:
While I am 100% sure Fatshark can come up with better ways to do this kind of mechanic I would like to see this or something similar that allows Psyker to use their full kit with every weapon available in ways unique to them, as well as carving out a niche for them in a team whether it is sustained/burst ranged or burst melee. All in all I would like to see Psyker be able to leverage their strengths to be able to, even if temporarily, surpass other classes.