I am a little confused. Does the mfg's brochure show a standard roof top unit? i have seen more and more smaller trailers using home window units. I can't say that i would rule one out because of it. I mean if it cools the trailer why not? super cheap to buy and can be sourced from Walmart i am going to guess that a removal and install would be prretty easy too. also, supposedly more energy efficient than the rooftop monsters. I don't see a disadvantage to them.
Some installs look better than others, i wouldn't want the coils exposed some sort of (exterior) grating would protect and trim out the install.
That said if your gut is telling you to walk on the deal then do it. there are plenty of other dealers and plenty of trailers...some of who may want to clear the lot before winter.
