In-game, a missile will be named "buoy" if it is an engineless, warhead-less missile with some kind of sensor on it.
I think it would be interesting to add an option when designing missile launchers to create a "buoy launcher." A buoy launcher would be smaller than a standard missile launcher, say 35 tons per MSP instead of 50, and don't require missile fire controls (you're basically pushing a button to drop a chunk of metal out of your spaceship at your own location) with the caveat that you cannot use it to launch anything whose first stage has an engine or warhead
Furthermore, a ship won't be labeled a "warship" if it has a Buoy Launcher on it
This'll allow more flexibility in designing ships whose primary role is buoy deployment/minelaying, while also making it easier to add that same capability to other class designs.
Furthermore, as things stand it's pretty simple to just slap a giant engine and a bunch of fuel to a missile stage and use that to deploy mines/buoys, I genuinely don't see much reason not to do so. Thus, the limitation of having a Buoy Launcher only allow for launching missiles without an engine or warhead while being significantly smaller (if I'm correct, at 0.3 size reduction, you're looking at 10.5 tons per MSP on the buoy launcher)
With the space savings on a buoy launcher, the gap between the space efficiency afforded by buoy launchers vs. the flexability offered by long-range missile stages used to deliver buoys and mines closes a little bit
