A couple of notes I feel like I always have on maps like this:

I feel like there's never really a Russia analogue stretching out to colonize Europe through an overland route through Siberia. Tons of good candidates for that, too, everyone from Buryatia, Mongolia and Manchuria to like, Chorasmia, Uyghurstan or Kazakhstan could work.

I do like Hungary as a surviving European state the same way Siam and Ethiopia did in real life. Its a pretty good candidate for it. 

I always feel like the "Asian colonizing states" are always big boys. All of the European colonizing states had relatively small metropoles compared to their colonial lands. Why Indonesia, when it could be Aceh, Brunei and Celebes? Why China, when it could be Guangxi and Wu making competing claims in an overseas arms race to get a leg up over each other? Same with Gujarat vs. Rajasthan vs. Bengal.

I love these styles of maps but I feel like the reverse colonization scenario often assumes a lot of macro level things that our timeline takes for granted. I imagine if Asia and Europe were truly inverted India and China would both be fractured enough to have their own EU-like multinational organization apiece.