You're right, a Star Destroyer and its massive crew and complement is really more than I need, and more than I would know what to do with. Not to mention, a Dark Jedi commanding a Star Destroyer seems unlikely. It takes expertise, afterall. So I'd like to opt for a simple Dreadnaught instead. The Dreadnaught's complement is 3,000 troops, but again I don't need anywhere near that many and I agree that the Second Imperium wouldn't throw away so many soldiers on some Dark Jedi's crusade. I think I'll go with 250, as you suggest, and a crew of less than 5,000 (which begins to flirt with being dangerously under-crewed, but so be it: this is the Remnant, afterall). Also a modest number of AT-ST's, no more than, say, 10. Dreadnaughts also have 12 TIE Fighters, and I think I'd need all of those.