I've also recently found the corresponding hero player model used in the character creation instance in the game files.
/Data/Mods/Main/Globals/Cyseal/Characters/players
this .LSB file contained 2 gameobjects named Scarlett and Roderick respectively.
I have since copied both Scarlett and Roderick and made Cassandra and Jimmy. I made them hero_player3 and _4 respectively.
Still caught up on the same MapKey issue though.