Mushroom Kingdom Fusion is a custom-made fan game (and not a hack, in case you were wondering) we have mentioned previously on the site, one which features a wide variety of playable characters and settings from many various video games. Naturally, Mega Man elements play heavily into it, including some stages and the ability to play as Roll, Proto Man, Zero, and Vile. However, neither the Blue Bomber himself (nor his futuristic counterpart) were playable. Zerothemaster passed along the following video update of the project, which not only explains why, but offers up some good news:
If you aren't interested in watching the first part of the video, then you can skip ahead to the relevant part here.