I think some kind of offensive use of the nemesis ships in response to champion progress would be fine... for you guys who are already pretty good at the game
I don't know how fun it's going to be for somebody who normally plays (and only sometimes wins) 7/7 to fire up a champion game, fly around a bit, and get stomped by a Sledge Hammer AI having a temporary moonlight as a Heroic AI.
That said, it's not a binary choice between "no offensive component" and "hammertime!". A balance could be struck, but it seems trickier to me than it appears to seem to y'all.
Fallen Spire has this happen to, in that I think a lot of gameovers happen the first time someone tries to recover a shard, or the first time they try to build a city. But there I think there's a better sense of "I'm asking for it", at least by the time they get to the city part.
But I see the balance-tension in that if I make it easy enough on players who just want to add a hero unit,
you guys will just grab the ball and run through the endzone, into the parking lot, and drive off with the AI's car