Why would you want weak hulled Starbases that are easily wiped out by abilities such as the Space Egg's Nano Disassemblers? While smaller orbital structures can take much more punishment.

Let me make a more exact suggestion:

Non-upgraded Starbase:

9000 Hull, NO shields

with level 1 defense upgrade:

9000 Hull, 3000 Shields + mitigation (there could even be a nice race against time to get the shields up before an attacking fleet destroys the starbase)

with level 2 defense upgrade:

10000 Hull, 4000 Shields, Armor upgrade, Shield/Hull regeneration upgrade

Keep in mind that Advent structures now do have shields and mitigation. It makes no sense a Hangar bay with 6000 Hull and mitigation is 3 times harder to destroy than a Starbase without upgrades.

The hull values should be proportionate to the size of the structure before any shield/mitigation concerns. Because there are abilities and weapons that ignore shields.

9000 hp base hull with no shields would be weaker than the current starbase. Nano-disassembler doesn't do much damage, but it does reduce armor, so even that ability would be stronger against a hullbased SB.

for the record, advent structure mitigation never goes above base. it doesn't go up to 57%+ like a SB, frigate, or capital ship