Basically think of it as a planetary Terror Star (if you ever played the first one).  You'd keep adding modules to it until it until you put a "Final" module on it that converts it's onscreen representation from a starbase to an actual planet. Until you actually convert it from a starbase to a planet with that last module, it'd be fairly useless.

So unfortunatly there'd be no fancy Planet/Starbase half-breed when you're done, but this is kinda what I was thinking for the Starbase design itself...

Which iconically kinda borrows from both of your ideas   so hopefully we can actually squeeze in time for this to get in and have the AI use it correctly, otherwise it may just be another fun idea that will have to wait

So yeah, sometimes it's necessary to use a nice stick figure here and there to get a simple point across.  Here we're showing (or trying to, at least) how small a human is compared to this Starbase.  The human is holding an apple that's inside a giant walkway on the outside of a medium classed starship that's patroling the lower left side of the starbase.

This is an example of artwork that advances the game in no way and was actually a waste of about 10 minutes, but at least now we know GalCiv2's worm-to-starbase ratio (143,637,807:1)