I would give the power bank 1200 energy storage along with its temporary slots.
My first justification for this change would be that it is called a power bank, yet it currently only acts like an extension cord.
My second justification would be that I've been trying to achieve the Drained L-Cannon without the Capacitor and more options to achieve that meme build would be fun.
It does already give you lots of energy storage, in the form of having so many power sources attached. Unless of course you're using Light or Micro type stuff, but otherwise you could store hundreds or even thousands via normal power sources or even Hybrid types!
Drained L-Cannon is meant to be extremely hard to fire. That is not going to change. Ever :P
It's not really even meant to be fired except by the craziest folks who can actually pull off an entire run dedicated to the extreme requirement for firing it in an unintended manner. The difficulty of doing so is set based on how hard it is, so making it easier in any way would actually just end up leading to increased requirements, defeating the purpose.