Gina, Escher gang leader (Necromunda). Don't mess with her or she'll kick your ass.. actually, she's gonna do it anyway!
Let's say I built a chokepoint, can I load all 4 starbases there? Or are starbases limited to one per hex like monoliths and orbitals?
No they're not. They are Ships in every way (except they can't have drives and thus cannot move).
So yes, you may build all four in the same hex to create a nigh-impenetrable fortress.. just make sure your opponents won't go around it, since once you build your Starbases, they're stuck!