This would be a good trial for the idea of letting people spawn submarines. As I recall HiTech saying, the idea for subs was that they could be spawned and then the spawning player could set waypoints for it. The sub would go on its merry way until it reached its intended areo of operation, where in the spawning player could jump back in and take command for the attack.
My thoughts are to do the same sort of thing with individual destroyers or even cruisers. The player spawning the ship could go away and come back later, taking command at any point. They could be of limited duration (dissappearing if the spawning player doesn't assume personal command at least once every so many minutes), with only a certain number allowed for each country. All the player mannable guns would be there, but only light A/I controlled guns would be enabled (precludes using them as automated mobile flak batteries). Just a thought, then would seem to be fairly straightforward to implement (of course, I could be wrong about this).