Elbeinlaw I see why your hitch guy might be a little gun-shy; that Airstream bumper is more of a 'roll pan' than the box-beam you find on the back of most travel trailers. It'd be a custom job, and not every shop wants to take that on.
A front receiver on the truck is probably the most off-the-shelf option. All bolt-on, nothing to figure out. It would also help the weight distribution on your tow vehicle. Our club SAG driver has a Sprinter with racks on both ends so he can carry more bikes, but the same thing applies. Downside is that your bikes are out in the wind, catching the bugs. (just like a roof rack)