If anything all Starbases and shipyards should have double or triple the values they have now.
Second that. Especially as the starbase military upgrades don't keep up with the power of ships and fleet sizes. The starbases become increasingly easier and easier to knock out so that a battle that should have some meaning is basically just mopping up.
My proposal would be:
- Modify the starbase building proximity rule so that a military starbase can be built in the radius of another starbase if that other starbase is yours AND it isn't a military starbase.
- If you attack a starbase that has in its radius other starbases and ships of the defending faction the resulting battle is against all of them.
This would allow you to surround a non-military starbase with a ring of military starbases similar how you build starbase rings around planets and it would also allow you to defend them all with shared ships giving a big synergy advantage.
I think you'd need a quite sizable fleet to defeat such a construction. As you should.