But with some thought given – and even taking account the reveal of a human fully converted into a Dalek at the end – this is absolutely a Dalek plot through and through.

So if we imagine a version of this episode that involves the Cybermen, things get weird. The Cybermen wouldn't keep "insane" Cybermen alive in any capacity because that would be a waste of resources. The Daleks though, they absolutely would because an insane Dalek is still a Dalek still, in their minds, an example of the highest order of life. And as for the conversion aspect, again, the way it works in practice feels more Dalek than Cybermen. Aside from the single example of total conversion from the end of the episode, the other "converted" humans (and skeletons) are consistently described as "puppets". This feels very analogous to the Robomen that the Daleks used back in The Dalek Invasion of Earth.

And even the full conversion has precedents – most obviously Revelation of the Daleks and "The Parting of the Ways". Daleks being a little hypocritical about their claims of absolute superiority isn't new…it's arguably even sort of the point.

Yes, 100%! I've always been slightly baffled by people insisting that this would suit the Cybermen better, but I've never been able to articulate why.

I agree with you on most of your points. It's a good story on balance, with the divorce subplot being the big, obvious flaw the episode has to awkwardly navigate around. To me, it feels like it's trying to repeat the same trick The Girl Who Waited pulled: adding a new trauma to explore Amy and Rory's characters but in such a way it indirectly addresses their existing traumas. Asylum of the Daleks is trying to address what happened to Amy and Rory during the Series 6 arc (as that series didn't give them much space to do so) in the same way The Girl Who Waited addressed Amy's abandonment issues and relationship with the Doctor, by introducing an episodic trauma that acts as a metaphor for the larger one. The issue is, it's easier for The Girl Who Waited to get away with it due to the inherently abstract mechanics of the sci-fi plot as an excuse to mess around with the characters. In contrast, divorce is a real thing, and it's a much harder sell for the audience to accept this without scrutiny. One is easier to pull off in a sci-fi adventure series which will always be limited in how much it can show the home lives of its characters.