IMHO, the ships are bought with money, not with how many players/members you have, so, if the people trade enough... why not buy a battleship?
On the other hand it wouldn't be bad thet the capship owners be at least the rank of Captain in the faction.
If the stars should appear one night in a thousand years, how would men believe and adore and preserve for many generations the remembrance of the city of God? - from 'Nightfall' by I. Asimov The Outcasts consider Siniestre Nube a sacred place for several reasons. Early explorers discovered a jumphole within the depths of the cloud that leads to a strange world of ringed stars and strange craft. All ships in the burrial ground are placed facing that hole to honor the Alien Spirits. - An Outcast rumor