The only one’s I really think need to be split are YRWA subspecies. The three look and sound very different.
Flickers would be my second in line. There’s only a very small hybridization zone.
Honestly, I’m fine with whatever the ornithologists decide. I don’t know enough about it, and I still document all the variation I see anyway. Whether it’s elevated to a species or lumped, it doesn’t really matter.
But I do have a problem with wanting to lump Bicknell’s and Gray-cheeked. We need Bicknell’s to be its own species so it gets the conservational help it deserves. I’ve seen and been in how little habitat they have left. I know I’m biased on that one though. I’m all for giving a subspecies or regional varient a higher designation if it means it gets more conservational attention.