5000 k, one battleship, 147 minions, 3 mod forts, and economic benefits. This is what you get from 10 nebulae.
The AI gets: a 20% increase to waves, reinforcements, and cpas, some bonus (I don't know exactly) to all exos, and the nemesis fleets.
I agree that you can get advantages from having a champion, if you play it right. I fail to see how, in any scenario (except the aforementioned all-the-way-through-FS one), this is severely unbalanced.
Definetly oppose them leaving the AI HWs at any point (except the aforementioned all-the-way-through-FS one).