I'm going to disagree with you there. Its not as if Mika invented "Dress-up" now is it? At the Prince gigs we were told to "wear purple"- I don't know much about David Bowie, but I believe he had the same sort of "dress-ups" going as well. It isn't fair to say that they are copying Mika if the idea itself isn't original.
Now if Mika wanted to patent something of his own- then so be it i.e. lollipop girl, big girl etc...but I don't see that happening. Why not stay as it is?? An idea, apparently, borne totally out of Mika's control (refer to TBA interview and Somerset House) and something that belongs to the fans. Or if he wanted to like he always has done, and not admitted to it, state on the tickets as a pre-requisite what the theme for the dress up should be??
It seems to be the "~controlling hand" that's going a bit too far- IMHO