It's a nice concept, but I feel it'd play nicer and feel amazing if you included some elements from Ghouls n' Ghosts. One of the amazing improvements in the game was being able to fire your weapon in any direction; left, right, up, down. Of course, you could only fire downwards if you were in the air. Your charged attacks (yes, Ghouls n' Ghosts had a charged attack) also fired in arcs around you, or otherwise covered parts of the screen you normally had no control over. I feel that would massively improve your gameplay. Megaman's levels is designed for his linear, extremely limited vertical mobility, while Ghouls n' Ghosts wasn't, having a much greater vertical aspect to the gameplay. Simply throwing Megaman into Ghouls n' Ghosts but half-assing both defining aspects of either game leaves a sort of unfinished feel to your game.
Megaman's defining aspect, I feel, is the ability for him to swap out his weapons basically at will, and for each of those weapons to have completely different mechanics. Without that, you just have a crippled Arthur in a Megaman skin.
Ghouls n' Ghost's defining aspect was the ass-shattering, brutal level design. You hated the game developers by the time you finished the game. Here, you just have a bunch of static, frustrating things. Take a look at a Ghouls n' Ghosts playthrough. The second level, if you can reach it, often makes you want to quit.
I know this is actually Ghosts n Goblins, but the later one improved so much upon the game that it actually became a fun experience, despite the difficulty.
