BASESHIPS?!?!
The largest I've ever put a colony comp on was a battleship. And I only used a BB because I wanted a colony ship that could colonize any planet type. Obviously this was late in the game when I could afford to throw away some resources to lessen the micromanagment a bit.
I did try role playing a hive race once that put colony modules in every ship. Didn't leave a lot of room for weapons though. My early ships were pretty much all set to ram.