That would take ages though and I don't think you can even reset data on official carts lol
Edit: Apparently you can but I seriously doubt most people would be down to do that lol
I tried doing 100% on call with @Frikkinfriks14 once. I did end up unlocking everything, but I ended up quitting before unlocking all of the staff ghosts so all that was completed was all the cups and mission mode, which took me about 6 hours 45 minutes.
I mean if you are going to go out of your way to unlock all of the characters in the first place, you may as well unlock all of the karts. I see where you are coming from when it comes to beating all of the staff ghosts, but these would be miscellaneous categories if anything.
don't you get rob through playing online? and since online is gone isn't it now impossible to unlock them all
All characters and karts are unlocked through Grand Prix, nothing is really unlocked through time trials (unless there are any alternative strategies that i am not aware of) so I do not know what the point of beating all staff ghosts being part of 100% would accomplish.
Well I guess unlocking other staff ghosts, you guys got me there. But to me, unlocking all characters and vehicles would classify as an 100% run.