You want to be sponsored under PNP? You will have to ask the PNP in your province how that works. It is possible that one of them can sponsor you even with you on an open work permit. If that is the case, you do not have to change your open permit, can still work for both and once you get PR, you can still work for both. If you have to be on a work permit issued to that employer for him to sponsor you, you would have to change your work permit and would not be able to work for the other one.