honestly the early culture faction abilities for the advent should be made at lower tiers.
Lower cost facilities for the advent rebels,
and the planetary culture for the advent loyalists.
in this way the advent would already be providing pressure against their opponents early expansion into their territory.
I suggest for the advent rebels to have their "cheaper temples of harmony" be an automatic cost decrease for that faction not requiring research. Also, placing culture at tech level 1 so that the rebels will be able to efficiently acquire culture relatively easily on the front lines. This would give them a much more unique start, and make the advent rebels also much more able to counter a truce among rogues.
Used offensively though this could be a bit overpowered(talking about the loyalists only).
So, in addition, make the initial cheap technology to get automatic planetary culture have a weaker culture expansion rate. THEN, add a higher level culture tech(tech 4 is a nice level) that improves this culture to become regular strength. In this way you won't have early expansion abuse, and this gives players more time to counter culture. The developers can allow the loyalist faction ability to be acquired early, which would make them feel far more unique, and the advent would better counter early truce among rogues invasions with their weak early game economy. I just don't want to see a one sided steamroll....
I for one enjoy the idea of truce among rogues, as it really mixes up the economic progression of the eco spot. Perhaps, every rebel faction in the game should have this eh? Then you could easily balance it. Just give it at different tech levels for each rebel faction.