Personally, I think that your Waltz sprite looks good enough as it is.
Of course, when MM characters are represented in the NES style (which makes them "small", mainly), one can't exactly expect them to be up-to-scale.
But, if you are still worried about her waist, you can tweak it a little bit.
That said, allow me to give you a suggestion for Virtual Man...
Since there may be fans out there that also have robot masters called "Virtual Man", I thought of a way to distinguish him from those ones.
How about giving him the nickname of "Pop"? Not only would this allude to the fact that he gets blown away/to scrap all the time, but it would be a subtle reference to his personality, which is a composite of a few pop culture elements.
Also, it would be fitting, since it blends in nicely with the musical theme naming of certain characters (e.g. Rock, Roll, Bass, Treble, Punk, etc). After all, he
is a failed Rockman Killer prototype, in a way.
So, what do you think of that?