Maybe I'm wrong, but reading the initial post of the OP it seems that the OP only lost the assigned seats. This can happen for a number of reasons; often equipment change. No ASR doesn't mean that the OP has been bumped from the J class cabin; most likely the OP is still confirmed on the AA flight to EDI. It would be very unusual for a carrier to offload the OP from the flight in advance even if the flight is overbooked in J class. Why should AA do so? If the flight is indeed overbooked in J/C this will be resolved at the airport/the gate.
So in my opinion the OP should check-in as normal and most likely the check-in agent at DTW will be able to assign seats for PHL-EDI as well - or the OP will be assigned seats at the gate in PHL. I don't get why we are even talking about rerouting here; most likely the OP will be on the AA flight to EDI in biz and if not, OP will be rebooked to another flight if needed or downgraded. The former is easily dealt with by airport staff and rebooking will be done regardless of award seats being available or not. But trying to rebook in advance will of course require award seats to be available like any other voluntary rebooking, but this has nothing to do with IRROPS on the day of traveling.