It never happened to me either, but it's there and needs to be taken into consideration. (It's a bit of a pain really.)
I figured it out. The facilities where I do my fighting (stores and personell, mostly) are indestructible.
Yeah, I'm inclined towards the same solution. But I guess we would need some sort of a drawback for not having the facility on base, to avoid the cheat with somehow removing the building to make more space.
Don't worry about cheaters. This is an optional mod. If they don't wanna deal with it, they can just turn the mod off. If they do want to deal with it they won't cheat (unless they are being
stupidsilly, and you don't care about silly people.)
That would require two different buildings, before and after the discovery of UFO Power Source... Perhaps the latter would be cheaper to run? (Pity we can't have buildings consume items on building.)
Nah, just claim that you are using an old power source from a pre-Xcom UFO scratch. It's been modified to output electricity only, and it does that in seemingly endless amounts, but they never figured out anything else about it, and the techs can't have it for disassembly since you need it for the power.
Or it's using a revolutionary new fusion reactor that somehow looks exactly like a UFO power source, aquired at great cost (or liberated) from a rogue nation. (Implying that the aliens have already had some success in infiltration and tech trade missions.)
Or it's just a general, non-revolutionary fusion reactor, but some joker thought it would be funny to make it look just like a UFO component.
Or it's a reactor of some kinds that just uses the rebuilt housing of a damaged power source, since even the housing is more effective at what it does than anything the humans can produce.
I'm sure there are other possibilities, but anything else I come up with now would be overly silly.
Remember - make the in-game explanation fit what you have in mind for the gameplay, not the other way around. Gameplay must always come first.