Burning Justice
the superior princess
It'd be a good choice, though it does violate another potential rule being one generation per cup since we know the Shell cup doesn't have a 3DS rep.
But when it comes to MK, I feel like they probably don't have a strict rule-set they follow anyway.
"Potential"? Every single retro cup in MKDS, MKWii, and MK7 follows the rule of "no two courses from the same game in one cup", and it's confirmed that the Shell and Banana cups from MK8 follow it as well. I very, very much doubt that that's a coincidence.
We already know they have a "don't use the same course as a retro course more than once" rule, no?