And I say a light cruiser or better because if you're sending somebody out beyond the borders of the Imperium by himself, there are certain requirements to be met if you want him to survive
I agree that around half of the ~30 or so named dynasties have LCs or greater but as the fluff suggests the existence of at least 60 Warrants in the Expanse, if not more, that changes the percentages somewhat. I always figured that the named dynasties represented only the most notable - the richest, the maddest, and the most archetypal - and that most RTs fell somewhere around the middle of the SP:PF ratio used during character creation.
As for Battlefleet numbers, well, Imperial doctrine would seem to suggest that most deployments would consist of 1-3 destroyers and/or a frigate or two to every cruiser. BfK lists most of the capital ships of the Passage Watch but I assumed there were three or four times as many escorts, as they tend not to have individual names - eg "Echo 2" for a frigate of Echo squadron or "RX-117" for a destroyer.
As always, though, YMMV; this is just my version of things.
Edited by LoneKharnivore