I don't normally reach out with feedback like this, but I really like this set.
Here are some changes I would like to suggest to the base:

For the novelties have you considered a couple of text novelties like "smash" & "go beyond"? Also, the smile or ears on his mask would be cool I think as a novelty. As for the current ones I like them but would suggest centering the "Plus Ultras" a bit more.
Including a spacebar kit might be good for those who use them.
If you're considering a deskmat then one with his lightning all over as a sort of pattern would be cool.
I hope this helps and best of luck

EDIT: I would like to suggest a single or pair of 1.5U Super keys for R4