What if certain ship systems had a passive thermal signature? Specifically, things like missile launchers that are loaded and ready to fire and power plants, specifically.
The former which, with some hand wavium, is another thing reigning in missile supremacy in specific roles, and the latter to a minor extent that full fire rate gunboats will be hot, where low fire rate reduced capacitor alpha strike boats would be slightly harder to detect, but may be largely helpless once it gets a salvo off. This also means certain ships are really hard to find when stationary, for example, small fighter ship with a basic sensor package onboard. As the ship only has engines and sensors, it can be invisible to passives as it doesn't have any "passively hot" equipment.
Perhaps we could allow a "stand down" stance to ships, that has weapons offline, which both sets thermals to 0 entirely, and also is noticeable on actives, so other race ships can identify that you've got weapons cold for diplomatic reasons, or enemy ships can see it as a wide opening to strike. "Weapons offline" would probably need a significant duration to toggle, of course, say several ingame hours, perhaps slightly delayed based on task force readiness. For obvious reasons, the ship would need to be expressing a "weapons active" signature while attempting the switch, in either direction.
Perhaps the "weapons online" mode could also have a specific affect on military engines, such that not being offline would make the ship slightly faster, less fuel efficient. That one's a bit of a stretch though.
