I've been pondering the same dilemma. Even though I only have 3 bikes now, our youngest children in several years will each have their own as well. The RV dealer told me about metal fabricators who can install a hitch mount directly to the frame of the travel trailer, avoiding the bumper mount failures. I'm looking around the area for fabricators that have experience with these racks.
I, personally, would like a rear trailer mounted rack as it would help even out the heavy loads up front in the storage compartment. Plus, no worries about lifting and supporting those bikes above the TV.
I know that Forest River makes trailers that have a cargo rack attached to the rear of the camper. I'm sure it's meant to hold a lot more than a spare, like our Bullets.
I'll let you know what I find in the Detroit area.