I have 3 spare relay slots. From what I understand, everything in the pdm plugs into the body control module via 4 large connectors. But once at the bcm, I dont know how I would be able to tap into them.
Pretty sure you have to de-pin the fuse box to get your wires where you actually want em and to get switches hooked to em. You could maybe talk to tazer about getting existing buttons program to do extra function if those relays are installed. seems like more work than its worth tho imo.
I would have to double check, but I think the open slots in the PDM are not even populated with pins. Even if they were, they would go down into a PCB that then would have to be traced to the specific connector pin outs on the back of the PDM.
I would not personally mess with it due to risk to other primary vehicle circuits.