A magazine block.

[Lurkily]

This would basically be a primary source of energy for your weapons; they'd use this block first.  Once depleted, it would be inactive until fully charged. (Just like reloading the clip of a gun.)  Weapons would be debuffed if they use normal energy sources; less damage, less range, less of every variable stat; say deplete the total after upgrades of each stat by a straight 40% across the board.  

Then, you have the benefits of using a SPECIFIC magazine.  You can have a magazine for fire ammo and cryo ammo and bio ammo.

They would basically be an energy block with a specific keypress to activate and deactivate them, and an output for when they're ready for use, or shut down after depletion to recharge.  I suggest an on/off control because a new player can add them to a drone, and they'll just WORK, starting out ON.  A more advanced player can use damage types and logic to activate damage types at need, and deactivate them when they deplete or when the need has passed.  Logic can help autonomous drones only try to use ammo types when they have awareness that a magazine is active.

[Epb7304]

I feel like this should apply to some weapons like the rocket launcher grenade launcher shotgun and blaster and they just couldn't use energy at all

[Lurkily]

I feel like that might be asking too much.  We're into an early public release now, and I think most of the core mechanics, like how fuel and energy work, aren't going to change too radically.  Making it a better kind of weapon energy seemed like a good compromise with current gameplay mechanics.