Ok....so how about the fact that RTP can only be called on a legal forward pass?
Good point. If you're sticking with IFP/IG, you'll need to decide whether to (a) wave off the RTP for the reason given, or (b) downgrade it to a PF.
If you wave off the RTP, you're back to a single live-ball foul. The IFP in the EZ would be enforced as a safety. If you make it a PF, you still have a double foul.
All that said, I'd rather wave off IFP/IG than RTP, if for no other reason than the LJ really shouldn't be flagging IG.