There's probably stuff we are still missing. Aren't there usually secrets we don't discover until a year or so later lol?
Classic costumes for playable characters does not equal "secret character". I think Skarlet and Kenshi would have rocked the secret character thing, then releasing them as DLC would be icing on the MKake.
I vouch for this. Remember when MKT came out for the N64 in 1996 and the UKK was discovered in 2007, eleven years after release??