That's effectively what I do. I have my dev branch, and then I make separate branches for each PR with just the commit in it. Works well enough so long as the commits are independent, but it's still a pain in the ass to manage.

That’s the trick in your system — all commits have to be completely independent. Generally mine aren’t, so unless we want to review each minor commit, they get squashed.

I can see merit in your suggestion, but it does require some discipline in practice. I’m not sure I could do it.

Perhaps I'm missing something... If your commits are not all independent - I don't see how could they ever be pulled/merged independently?

The way Gerrit handles this is to make a series of PR-like things that are each dependent on the previous one. The concept of "PR that depends on another PR" is a really useful one, and I wish forges supported it better.