I think it's been discussed before, and it would be unpractical on larger maps.

I'll just say, please don't.

I'd love it. Pretty easy to carry a constructor along for an instant starbase, and since I never invest in life support techs I have to do this on campaign anyway.

I've rarely needed to move up to Large hulls but my current game (large with lots of planets and stuff) may prove an exception. Usually I can tech my way up and pack a lot of stuff into a medium hull, then deploy 5-8 of them in a fleet and steamroller whatever the AI can put up.

In this game I tried splitting my mediums into an escort 'tank' class with lots of defense and little or no armament, and a capital 'shooter' class with lots of beams and missiles (taking advantage of the events that more than doubled the amounts of AM and Elerium on the map). However... while enemy fleets seem to follow priority rules and not fire on capitals until escorts are gone, starbases evidently don't. So my careful prep of having a spare escort following my fleet to replace the damaged one and keep the offensive moving - well, that foundered when my undefended capitals got shot up as I took out starbases. So I may go back to making generalized frigates.

By the time I can research targeting I'm usually better off going for carriers - assuming I need them. Plus, I've never played as Thalan. Maybe some day.

Look through the existing threads. I think someone has a mod that increases repair at starbases and planets.

As far as I know, it isn't.