I just want something to discourage you getting that with one HW. The nemesis feel like half the puzzle to me. They become mobile core posts if you have 150ish aip when you attack the HW. So you treat them like core posts. Knock out one or two, retreat, rinse and repeat. I don't see that as anything more then a time sink.
They easily doubled the difficulty of the HWs. It is quite hard to take out an individual nemesis, in the face of overlapping shields, and they are too fast to engage them individually for more than a few seconds. They also make it really difficulty to, say, take out CREs before anything else. Also, said time sink is more expeditions to the AI homeworlds, which also alerts all the core worlds, and more time for things to go wrong while your fleet is away.
And then there is the difficulty of actually getting to all the nebulae (deepstrike, raid engines, SF). I know there are ways to do it, but it is not trivial. And if it is really easy, that probably means a well-connected map, reducing the value of the mod forts, and making FS a royal pain.
Makes the middle game too easy? Increases endgame difficulty enough to compensate.
No offensive response? .2 HW count makes waves a little harder and planets somewhat nastier. But it really shines in CPAs, where it translates to ship numbers in the thousands. And then it gets more for every single exo.
So I really see no issue with the AI champion response, except that one FS-endgame tweak (
here).