So, my colony is currently made of 7 pawns.
I have now got a quest about borrowing 7 (so all of them) of my pawns to the empire to destroy an enemy outpost.
Accepting I would leave my base defenceless (even if for some hours), has ever happened this to anyone?
It happens at times, especially if the size of your colony remains small, but I generally don't find it too problematic. Usually able to overwhelm the enemy outpost fast enough that even if an attack were to happen I would be able to get back to intervene, transport travel time is negligible after all. If you're too dependent on supporting a frontline defense system to get through a raid then you need to consider internal defense measures anyway.
The time your base is defenceless is pretty small.
You get an Air-taxi to the enemy base, and you get one back.
You don't even need to gather the loot, it get auto-collect like at a caravan encounters.