I agree with your diagnosis, not with all the solutions.
This is correct in principle, but I do not think this mindset is one that should be put forward. I do not play this game as a competition to get kills, though this is extremely frustrating :
It’s not about not getting the kill, it’s about feeling useless and outclassed in every regard.
Psyker in general is completely underwhelming on his own, and even more so when compared to the team. Everything takes ages for very little return : by the time I charge the surge force staff, the enemies are dead. By the time I finish casting BB, whatever I’m targeting is dead. I use force sword special : I’m locked in 2 seconds of animation and get hit. Even when I get to cast lightning, the damage is bad.
I have to manage a prohibitive peril mechanic, which other classes do not - I mean that I can use a combination of 3 spells/BB/force sword before needing to vent and not contribute to anything for a couple of seconds. Even the slowest weapon to recharge, the pistol revolver, is in the Psyker’s kit.
Back to your rework suggestions :
I have made a post suggesting some BB changes. My version synergises with the elite damage in coherency and allows warp charges to remain mostly the same, despite being mostly useless.
That being said, since BB is a grenade slot, it could make sense to be a “consumable”, meaning requiring some kind of resource, like warp charges. I have also read a suggestion about having warp charges empower BB (against elites and specials) instead of being a flat cost, which I think would fit in well with your suggestion.
Warp charges should do more than just “be there”, like decrease casting time.