If only you had the time to do this...
I love this idea! Especially that one stage from Megaman 8 where you probably got the inspiration from.
Seeing as now you have a game in development and a redesign on the way it looks like a sequel will never come. But I got a few suggestions.
The devil guy from Ghouls and Ghosts
Gutsdozer
M.Bison
Assist Powerups like Auto and Beat.
Uh that's all I got
Anyway I hope you make a sequel of this fun addicting shooter. A great spin off of all the Megaman games!