Just a snap suggestion; what if CBMs worked sort of like engines in cars? Anything that has an active or passive effect is fine, but while your first power source is super easy to install, every one after that gets harder and harder.
This sort of pushes a character into a playstyle until they can get the electronics skill to put a different source in, and it means that even mid to late game, you still have to think about where your power comes from instead of having a solar-ratchet-metabolism monster thing going on.