Theoretically you could just use the things present in Kart itself for characters, that is to say, disable Sonic/Tails/Knux in Kart and only enable the versions that actually support it. It'd nullify the need to bleed the frame naming convention dry of the UNI alphabet.
Although peoplemight would complain about the characters present in Kart not being playable in the regular modes, ultimately.
Although people