Thanks for the standing order propagation options. That will be a massive help.
I have a question about the enhanced precursors though - Since there is a delay between the emergence of ground forces and space forces - What happens if all ground forces are eliminated before the space assets wake up? Do they immediately activate, or will combat on the surface immediately trigger the space assets as well?
Since the justification for the delay is for the precursors to secure the surface before launching their space assets, it would be a bit weird if they didn't react to losing the ground engagement and just waited with their space ships. It would also be cool if your forces could potentially discover the dormant spaceships in such cases.
I was wondering if someone would ask that 
As it stands, if you destroy the ground forces, you capture the colony and no more ships appear. I haven't decided yet whether to leave it that way.
It's a tricky question. On one hand, as it currently stands it could be pretty easy to cheese the "Advanced" Precursors if you get a couple divisions of troops on the ground and never give them a chance to launch any ships. On the other hand, as noted it would feel silly if defeating their ground troops didn't impact their ship launches at all.
What about a different mechanic that calls back to the old VB6 robot soldier events while excavating the ruins? Excavating a ruin site which might have Precursors has a chance to reactivate the guardians, either a ground combat formation or an ancient ship (or several?) that had been offline for millennia. That way, the lore doesn't imply that defeating the ground forces will impede ship deployment, but you still get that gradual danger that requires a long-term commitment of forces to obtain all the nice, valuable loot.
I considered the original VB6 robot army mechanic to be problematic, since the resulting combat tended to destroy a lot of the loot from excavations and led to some rather cheesy strategies to prevent this, but as an optional mechanic I think it can work well as long as the player knows what they are consenting to when they click that check box.

The other possibility might be to make an exception (a dangerous suggestion, I know) and have Precursor ground forces do zero collateral damage, which is maybe less realistic but more rewarding for the players.