We can't really like posts, so I'll just put this reply. I think a new Mega Man Halloween Hack is a phenomenal idea! It has been far too long since I have played a new Mega Man hack.
If possible, I think it should be a hack of Mega Man 6. MM6 has a multitude of great content as it is, and would allow for creation of new abilities and diverse routes for each stage. Adding the ability to slide in Power form and Jet form, along with not losing charge when hit, add charge in Jet form, and Double Jump and Air Slide abilities from previous hacks would also make for great additions to this hack.
Players want freedom of movement and earnable special abilities. Give it to them. And make them usable. Add new routes to each stage that requires these new abilities to get to. And make the rewards worth it. Look at MMX2 and all the headaches you had to go through to get the Shoryuken (Fire Punch). Make third level charge, and quick charge, power shield, knock back barrier, half damage buff, speed shot, 5-shot, Jet MM Upgrade, and Power MM Upgrade as some of the rewards earnable. Make this Mega Man Hack the best one ever!
Use memorable music tracks. Some old, and some new. Tracks from memorable horror games with catchy tunes like: Castlevania 3, Zombies Ate my Neighboors, Monster Party, Nightmare on Elm St., Remix of Shademan's Theme, Spooky areas from Non-Horror games, as well as some new horror based songs.
And for once, make Wily NOT THE FINAL BOSS! You could make it seem like he is the final boss, but make a "True Ending" in which the player must fight the "True Boss". Again these are just suggestions and I know it would take a lot of work to do something of this caliber. But I have seen things like this done already. We could give Blue-Bomber fans something they have always dreamed of.