I've found processes like this to work better, too. Basically, the one big pr is like building a prototype to throw away. And the benefit is it has to get thrown away because the PR will never pass review.
Yes, though it does depend on how good the commenting system is; and, for something like that, you're still probably going to want a meeting to walk people through such a huge change.
And you'd better hope you're not squashing that monstrous thing when you're done.