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.