I use BaseSizeAdd=170 in my mod. It stops applying after a point, for reasons I'm can't put my finger on. And it's not just the base defense limits, either. I have
MaximumBaseDefenseValue=3500
SovietBaseDefenseCounts=120,120,120
I've really hammered this aspect really hard, because I wanted to get the AI to build an /enormous/ base, and then tune in reverse until I felt it was the right size. It's not that easy getting to an enormous base, IMO. It's almost as if it loses interest in building after it gets to be TL=10.
But I didn't quite understand what you're trying to achieve. Why do you want the invisible refinery unit to "guard," exactly?
Anyway, while I haven't tried it, if you made the AINODE behave like a conyard, why wouldn't the normal "second conyard bug" not apply?
Observation: if you set IsBaseDefense=yes on non defense buildings, the AI likes to build /real/ base defenses next to them. Or at least I believe I've seen that behavior. Bit wierd, that. I'll have to experiment more with it.
C
[ADDENDUM]
Here's a snappy of what happens when you give AINODE1 a free invisible slave miner clone that produces a soviet refinery. The thing I was worried about ... that it wouldn't work without a script ... turned out to not be a problem. Slave miner copies seem to have a life of their own:
