Instead of overheating like they do now, weapons should instead start to fire at a lower rate, as to consistently keep the heat at max without going over. For continuous weapons like lasers, they should just become slightly more transparent and deal less damage proportional to their overheat boundary.
So basically if you are continuously firing your coil mortar, once you reach the maximum heat capacity, it should simply start to fire at a much slower rate, like it’s firing one shot then waiting for the weapon to cool before firing the next. This way you can keep firing at max heat, but it’s just very ineffective.