I do not know if this will work or not in your case scenario, but i was trying to see if i could implement it in the mod i hope to finish one day.
We all know that heavy plasma are the weapon of choice from mid to the endgame.
So i was thinking a system for preventing the user from directly using the weapons, with the excuse of human anatomy, dna based security whatever you want to call it.
So you will have Alien Plasma weapons and human plasma weapons.
humans are not capable of using Alien plasma weapons. However Engineers have been able to dismantle the weapon into 3 component, power cells (ellerium cells whatever), containment chamber and alien alloys
disassemble
plasma pistol produces 1 of each
plasma rifle produces 2 PC, 1 CC, 2 AA
heavy palsma produces 3 PC, 1 CC, 3 AA
or whatever number you want, this are just examples.
with all the components our awesome engineers can now start producing human plasma weapons.
Production cost
Plasma pistol = 2 PC, 1 CC, 2 AA
Plasma rifle = 4 PC, 2 CC, 5 AA
Heavy Plasma = 8 PC, 2CC, 8 AA
with this you can keep your engineers busy, not have money out the ying yang and your stockpile of weapons will be drastically reduced.
just an idea, i remember i posted somewhere in here, but it was too long ago