Oh, if I wanted that sort of thing, I'd be using my sensor drone design, but I'm saving that for my second generation of stealth/scout cruisers, as it mounts a fairly heavy package, and I plan on using magazine storage for them. The buoys are specifically intended to help destroyers fill their ideal role as frontier pickets and protection of commercial shipping. This way, they can drop buoys at nearside JPs, and sit in a central position on picket (likely with a small ammunition depot with maint. facilities for reloading buoys somewhere in-system). Once they get a hit, they can go active and respond to the threat. If it ever comes down to another assault on a hostile system, I'll be bussing in a few score FACs and frigates, as that worked fairly well last time. Of course, by the time I finish digesting Basil and Manticore, I should have heavy enough industrial capacity to start putting out light cruisers, so destroyers should ideally never be my mainline force, except out of desperation. They're there to keep an eye on my borders and pick off survey ships and light enemy forces.
Of course, once I get the tech to put up proper carriers and fighters, the destroyers will be intergrated into a larger defense doctrine involving highly mobile light forces that can harry and raid enemy shipping for long periods of time. Hell, I may even invest in hyper-capable carriers, gog knows I have enough massive multistar systems.