Well lets look at the options. Clans build only the Fredasa, York, Conqueror, Nightlord or Leviathan. I'll assume the plans
and at least one slip are available one way or another.
They'll build these ships or upgraded variants of them in the best balance between numbers and cost - Leviathan being what it is, maybe it's out of reach, but there are tradeoffs between building say 2 Nightlords versus 4 Yorks etc
That or sink funds into an all new Clan warship class or two, preferably a Castrum-killer that can liven things up a little. I'm sure we'd all like that.