How about the possibility, that some high energy weapons, like heavy lasers, plasma cannons, or other heat producing weaponaary, could fire a lot for a short time, but causing it too overheat.
this is just a real life phenomen, that could stand for the long time of refiring of for example the annihilator gun.
Also could this overheating be possible with the possible anti-nuke laser defense system. Which first of all uses a constant huge ammount of energy (-1000 per sec), but can also get overheated, when multiple warheads/nukes/emp missles close in. Maybe the option to build extra cooling systems on this defense building, or some otherway...
Just some thoughts about the possibilities of overheating. Those high energy consuming lasers and plasma weapons must produce high quantities of heat.
In addition this could be nice with the possible upgrade system. You could enhance the cooling methods, and there giving it a faster reload time. But the upgrade system is still in debate...