Hey that idea with the wonder seed changing up the stage/race track sounds awesome.
I was thinking more on transformations on the kart.
Whatever they choose - I just care about the following
-More Mario characters (probably add Kirby to the mix)
-More new stages (and bring back older stages like MK8D did)
-More items
-More customization items for the kart
-The ability to modify what items you can use in single player mode (like they did with Online for MK8D)
-Story mode/open world mode like Diddy Kong Racing