Nope, all 2nd gens and most newer imports require the use of relays or else a splice job will fubar the electronics and burn stuff down.is there not a T-harness for the gen 2s like the gen 1s have?
You can probably do the bumper thing but I am not sure how much the trailer would be jacked up. I would try and stay off the interstate or major roads if possible.
Purchasing the relays separate is going to be hard to do. I don't think anyone has sourced who makes them for Nissan so finding the correct ones that just plug in will be hard. Maybe an electrical supply store near you will have the relays?