There is no official way to do it, but there is a work around.
You need to open multiple instances of the game and create a multiplayer game by yourself.
Its worth mentionimg that if you dont plan to make full custom party ... it may cause problems with your relationship progress.
Bcs game conciders characters created this way to be PC Avatars even if they are all controlled by single person.
And therefore your companion dialogues are sometimes overwritten by PC conversations.
Like i for example plan to make full Gith party ... i tryed workaround in EA for that ...
And in Druid Groove, after Lae'zel talk to Zoru ... instead of talking to Lae'zel about her integoration techniques ... my "PCs" talked together and completely forget about her (meaning i wasnt able to talk wirh her even after).
So ...
If you have simmilar plans, lets hope we will be able to change races of Hirelings.