Thought about this a bit more because my brother and I were talking about this not too long ago.
Having recently played some more action heavy metroidvainas, games like Afterimage, Ghost Song, Touhou Luna Nights, and others, I think taking mega man in a Metroidvaina direction could be really amazing.
You can still keep, let’s say 8 bosses, and absorb their powers as you go, but now the boss powers are weapons and/or abilities that help you and fight traverse the map. The maps can be roughly divided into 8 areas for each boss,
And you can still have the multi stage “Wiley fortress” area as well. There’s also those Dr.Light Canisters from Mega Man X which power up your armor in that game, but could be put to all sorts of uses in a metroidvania setting. Could be a way to make it so bosses always give you a weapon, and other upgrades come from the “canisters/tubes”
Other action heavy games have shown and both projectile combat and melee combat have huge room for various gameplay mechanics, counter mechanics can be nice and satisfying, as well as all the usual shit like dodging, etc
And of course plenty of platforming, wall jumping, etc the foundations of all those moves have been in since like mega man 2, and mega man X just dialed it all up to 11.
I know it would certainly may get my attention if they did a mega man in this style. And it can be sprite based! And sorry but none of that horrible NES shit, we either go MMX style or MM7/ Power Fighters style
I can’t tell you how disappointed I was when MM9 came out and they went back to NES style.
I grew up with that shit, it’s not hip and retro imo, it looks like garbage from limited technology, and was just the best they could do back then.