There is currently no way to make any changes to the game while still in it. At best, you would make a series of character.xtbl files to change the player's model to Zinyak or any other model, and swap them out depending on which person you felt like playing as.
Though, it may be possible to use the Mech function that you unlock at the end of the game. The way the mech works is that you call it on your phone, and then it swaps the normal player character for the mech version. What if you could add a copy of the mech on the phone list, but replaced the part where it transforms you into a mech with a part that transforms you into Zinyak, Shaundi, etc?
The only trouble is, I have already tested this out, but it was severely bugged (character was missing head, weird behavior, etc). Until I or someone else can figure that out, model swapping and what not is out of the question. But hey, it's a step forward
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