As i already mentioned regarding standard weapons, soliders don't fire that much in a given encounter.
About new technology and plasma alien weapons I don't think neither you nor I can tell
anyway, still as already mentioned, it's not productive right now to mess-up the well-made balance. Overheating right now is useless. If in the future comes the need to differentiate weapons beyond AP cost, damage, range, accuracy, overheating could be the missing variable. But not rigt now.
So I agree, after a few more hours of play - now it's useless - but don't say complicate. A gauge depending on a single dumb variable (shoot vs not-shoot) can't be complicate any serious turn-based strategy player. It can't. Useless, not complicate.
About fun it's quite subjective... More variables mean more complication, more problems but also more opportunities. And overcoming problems with opportuinities is my (subjective) source of fun.
The same thing you said about overheating could be said about morale of soliders. Useless complication? try to think the game without it. It would be more deterministic perhaps. No more sudden overthrow of results. Funny? Subjective.
Why don't you protest then about localized damage and bleeding? It's a useless complication, the old fashioned health bar fits perfectly. Or not? Not for me
Anyway, i put ideas on the table, but i recognize i am not the one who follows the development of this game from early stages, there are many variables i don't know. "I know i don't know".