If we moved Monk to the bench for Fultz, I'm 99% sure that he would actively revolt. Like, Monk firebombing G1C would not be out of the realm of possibility (OK, maybe a little beyond the realm, but you get my point). So, like, you can do it, but the consequences of doing so will almost certainly be worse than the benefits.
Monk's best role in fact has been as a 6th man spark plug, but I am quite certain that Monk does not believe that, and that's what matters.