All Cups Itemless ? It would be fun, of course... But it isn't possible. MK7 doesn't have VS mode for Single Player :v
And 100% requires to reset the save, which is impossible... :/
50cc would basically be more a slowwalk than a speedrun Kappa
But Mirror can be interesting :)
It would make a pretty good run for a 24 hours marathon XD (But you wouldn't have time to do anything else lol)
What about a All Cups All Characters All Modes (50, 100, 150, mirror) category ? The challenge is to stay alive during the 110 hours run Kappa
The maximum time you can submit is 100 hours. That might not be enough for all cups all characters all modes.
Without using items? that means no mushrooms. Having to do shroomless versions of shortcuts would be fascinating.
This would be a separate category, just like the Hoverless runs in Super Mario Sunshine. Of course, there are a few shortcuts/glitches you couldn't take/execute, but that's what would make the category different.
It would be a nice addition to the unofficial leaderabords though, I had completely forgotten about this one.