I have a few ideas for this problem:

- There should have been more penalties for having a starbase on the territories of others. The owner of the area should be able to tax the starbase, both it's economy and resource.

- The tax rate should be optional by your own choice. Taxes from 0-90% or more would be great. And other political penalties which might render a starbase to be a full loss for the owner.

AND / OR

- Introduce politics where the owner of the territory will be the owner of the starbase (built by another civ), but you must negotiate a rate of sharing the resource and economic gains.

- You should also have to negotiate before building military and influence starbases in another civs territory. If not it's an illegal act, and might trigger a war.

I rather like the idea of a tax on a SB in one's ZOI.   And a right of refusal for military and cultural SB, with the consequence...WAR...what's it good for?   Getting rid of starbases, of course!

+1 on this idea. I also wouldn't mind if it was adjusted by life support tech, so makes those techs a little more attractive.

I like this:

I also think starbases' defenses are far too powerful in the early game with no way of removing them for quite some time.
That's how it used to be, I would fear for their safety until I upgraded their defenses.

If they didn't receive attack / defense points until you actually researched the required weapons / defense tech's, that would greatly help the problem in that I'd be able to simply wipe those pesky star bases out - although you shouldn't realistically place a one near a potential enemy then (The AI would have to factor that in I guess) - problem solved another way.

also i noticed that starbases are too strong.. in civ2 starbases were not too strong.. for example you could bulid tons of constructors and focus on huge reseach for starbases and decent ship could kill it.. and now?  with two constructors you get like 10 of each defense and +15 of each attack much strong