sorry for the delay but i think it may be possible to set the E_MODEL you're using to replace model to be a different value: (this is experimental even i don't know if this will work)
basically, whenever you start a game the model you used is set to a local variable at the beginning, so if you were to put a script that detects if you want to use a gustavo section, and then set the e_model variable to the gustavo model, you should theoretically be able to set the model. don't quote me on this...