Well, I know that most of the robot masters have some kind of natural power, like water/fire/ice/rock/speed/timestopping/flying/whatever, but there are still many options left. And Sheepman actually splits into CLOUDS. If it would be Sheepman, it would shoot fur bullets that blind enemies or something. But this feels like Capcom was "Okay, we have only 7 robot masters, so let's copy some of the old ones. Okay, Cloud is cool, just give him some other name because Cloud Man II sounds stupid. Brainstorm. Cloud is fluffy. Maybe something fluffy. Sheep. Sheepman. Sheeps don't shoot thunders, so let it split into clouds. Clouds shoot thunders. /topic". Okay, maybe I nitpick too much here, but I'm certainly not like "OMGZ ALL BOSSES HAZ BLACK OUTLINES PLAGIARISM!!11!!eleven11!". Similarities are fun. Copies are not. Maybe many companies are doing this, but also many people kill and steal. You can, but you don't need too be like them.
Wow...okay, where to begin...
First of all, the idea of SheepMan is the idea of static electricity, just RM'd pumped up to lightning status. Second, you just disproved your own "ripping off" theory with SheepMan, as CloudMan does NOT split into 4 clouds, therefore making SheepMan not a rip off of CloudMan. Third, clouds do not SHOOT thunder. They shoot lightning. Fourth, the idea that these games are ripping off older MegaMan ideas is just plain amazing in itself. Um, you cannot rip off your own company's work. If the games you are ripping off are games that you own, then it's yours. It would be different if Roll showed up wielding a Superdragon, because then she'd be ripping off Perfect Dark.
And finally, this game has Playable Blues from the start, so every single thing you mentioned doesn't matter.