Honestly, why hasn't there been any sort of five star Winmillion?
This has probably been asked many times, but I don't know any answers that aren't "lack of interest" or "just get a striker". I know the Winmillion currently isn't very strong, and honestly even with a five star variant it wouldn't exactly be trendsetting for the current meta, but I personally would love to try it out. It's relatively unique in the way it hits and, for what its worth, I think a lot of others would love to see it finally reach that point. I wasn't really sure if I should ask this at first, however, since GH decided to turn the Cautery sword into something workable I figured it couldn't hurt to ask.
The problem is that you can't just create a 5* variant and be done with it. You have to code in new mechanics and test them and all of that. If you don't do that you just get another cautery incident where you create another "trap weapon" that no one ought to want.
Winmillion in particular is in a tricky spot- if it does "good" damage it will be too powerful given its range and ability to close in on things. If it's balanced around this (as it is now) it will do not enough damage and no one will want it. Hence we need some kind of mechanic change, whether that's even larger distance covered during the combo, a long range projectile that does status effects, a better charge.... etc.