(Not the mod) Having a prosthetic limb doesn't qualify for the exchange. It's in the first paragraph of the rules: https://turingfest.dreamwidth.org/11282.html#cutid1

The reason why 'Keith/Shiro & the Black Lion' were accepted last year is because the Black Lion qualifies under 'AIs, robots, androids, mecha, machines, cyborgs, and any other technology-focused characters'.