Modus ponens is basically to the effect that you can infer it if it follows.
Without it, you are in dry dock, inference-wise.
Of course, you can always tinker with the way it is expressed. Instead of saying
you can say:
-((-P or Q)&Q)&-Q)
But given that ‘P->Q’ is definitionally equivalent with ‘-P or Q’, this isn’t exactly a way to get rid of modus ponens. Same holds if you try any other work-around.