As you will find, there are many different options for carrying bikes other than the rear bumper. Some options are...
receiver and bike rack added to front of tow vehicle
roof rack on tow vehicle
bed of pickup truck (if you have one)
rack mounted to front of trailer (many have custom built their own...any good fab shop can handle this)
inside of trailer (some RV'ers add mounts to the floor or dinette area)
IMHO, about the nicest bolt on solution is made by Arvika up in Canada.
. I built my own rack very similar to their 5th wheel version.