But one would not suffice, since it would still enable you to buy all weapon and armor upgrades. If it is to be upgrades I would opt for making the Stabilizer Upgrade 2-tiered and Phase Jumping available on the second tier. Thus either damage or armor would not be on maximum level.

You would trade raw combat strength for mobility if you wish to do so. Just a thought though. 

Yes I know, it's sad and doesn't make sense.

But I had modded it in once out of interest. Which led me to my claim that 30% does nothing to balance the Orkulus whatsoever. 

Well thats the thing about starbase upgrades, it doesn't have to take only one slot. It can take more as to limit what other abilities the starbase can get. My point was it should be set up to prevent getting level 3 on both weapons and defence.

Make it an upgrade that would eat at least 2 upgrade slots, and eat 50-100 fleet supply.

Just a thought perhaps we are going the wrong way about this orkies have always been strongest star base ,perhaps buffing the other designated anti structure units would do more to limit its abuse, perhaps in allowing them to bypassing the armor bonuses which seriously limits their damage to the orky late game and the other factions star bases could buffed slightly more health/shields to offset this. (they also need to add at least 2 prerequisites to technology tree to slow people from rushing to it too early in the game but that's a different issue.) the real problem is the counters to the orky are not effective enough to even threaten a fleet supported heavy armored  orky in a gravity well. it that or add some long duration debuff that limits it effectiveness or movement after jumping to slow down the starbase creep or leave it vulnerable to focus fire perhaps all of the above is needed but improving the other factions ably to counter the orky jumping or otherwise is better than limiting it with fleet supply which will just be a nerf that essentially remove the feature and the unit from the game when the failure is the ability to counter it is too expensive and not effective enough.