There are
a few great ideas in this thread, including a frame welded hitch and bike carrier. Four bikes is a lot, so you might want to "divide and conquer". I put two bikes in the bed of my TV and still have plenty of room for gear. The other two bikes could go on the TT bumper, the tongue, inside the trailer, etc.
Alternatively, I've seen people carry more than 4 bikes with the front wheels over the tailgate using one of these tailgate pads. The pic is a link to amazon, but there are many similar.
And you still have room for gear in the front of the bed. As a bonus, you don't have to remove the front wheels like I do with my "fork mount".