This game mostly encourages playing one hand type, and actually discourages playing more than one hand type in many cases.
Supernova is one such case. If I have a High Card build going and I happen to draw a Royal Flush, I don't think "oh cool, a Royal Flush", I just ignore it and play a single 2 and keep growing my High Card hand count in case I find Supernova.
I propose an alternate Supernova that gives 10x the hand count of the 5th most played hand as mult. This would reward players for playing a variety of hands. (Players would have to play at least 5 different kinds of hands repeatedly to increase the mult.)
This could replace Supernova, or be a new Joker, and the exact numbers and balance might need to change. That's all up to LocalThunk, but I wanted to suggest the general idea.