How to unlock Vanilla cruisers Type B & C?
solved (I think): unlock any 2 variants of 1st ship of each race (not the ones on the vanilla cruisers page of course) to unlock type B of vanilla cruisers.
To unlock type B you need to win with type C.
To unlock type C you need to go to sector 8 with type B.
So there has to be another way to unlock B and/or C first.
I just won with the Hive Cruiser Type C (normal victory), and it unlocked Vanilla Mantis Cruiser type B
edit: happened again with Theocracy Cruiser. So most likely unlock any 2 variants of 1st ship of each race to unlock type B of vanilla cruisers.