(This is sarcasm, not a suggestion...or is it...)
I know what the Winmillion 5* upgrade can be. It shall be called the Rommillion ... named after Unity's mascot Rommil.
Each strike shoots out millions of crowns, because, let's face it: Rommil's rich.
And the charge shoots out three text bubles that say: "Rommil". ( http://forums.spiralknights.com/en/node/53402 reply #12 so you get the reference.)
Every burst of Rommil and charge attack deposits real crowns onto the ground which can be picked up....and of course donated to Rommil.
(The sarcasm is over...or is it...)
-Lanieu
I laughed xD