One idea that I had is that most Clan's fleets and pool of crew/officers for WarShips is actually quite small.
From the fluff and lore we know that for the most part, the Clans tend to hold a somewhat dim view on WarShips. So those Clans who are of that mind, instead of having their WarShips active all the time, the vast majority of them are laid up in mothballs. With only a few ships active at any one time.
This would allow them to reduce manning requirements. And active warships 'share' crew. IE for 6 months you might be assigned to a Vincent class, then after that, you're aboard an Aegis.
The warriors who are the ships officers are probably going to be aerospace phenotypes for the most part and these are older warriors, not Solhaman but heading that way.
And if, in times of serious trouble, say the threat of a Trial of Absorption or something, this kind of event would take a long time to arrive so the Clan could have the time to reactivate any ships and get crew on them if needs be. But i'd guess that most Clan's couldn't fully activate every ship in their Warship fleet and give it their complement of fighters etc because the Clans have major manpower shortages.