First, I would not want to call anyone retard.
But here is the thing about Mega Man. They decided to create the game with the feel of Mega Man 2...which means that for this game they decided they wanted to leave out abilities that Mega Man has had for more than half the Mega Man games available.
I actually respect that decision, because many people feel that Mega Man 2 is the best game available in the series...and if you want to play the game in those options then that is exactly what you can do and buy just the single game.
Now, if you are like me and want to play Mega Man with Slide and Charge because you like the feel of the later Mega Man games, paying a little extra for that choice may not be a bad deal...specially if it is only $3.00.
And yes, I don't feel that you should be paying for already coded stuff...but for new content, levels, enemies, bosses.
And I really like your description of opening up levels and such...it is how I envision it.
Truthfully, I just want to play the ultimate and perfect Mega Man game...and I don't want the game to end if I don't have to. So that means.
I want to play as traditional Mega Man 2 Mega Man, but I also want to play Mega Man 4-6 sliding and Power shots, and Rush Abilities Mega Man.
At the same time I would love to explore controlling Protoman, heck even have a Mega Man Protoman two player mode.
New levels, enemies and such are a must, because with retro graphics they can make an infinite supply of levels and it not take up too much space for the Wii.