Get a remote start 3000 from Honda and you pay almost the same as an Onan but it still will not be built in. Unless you specify your TC with low power draw AC, you will be buying two companion 2000's plus the additional interconnection cord. There are options for everyone...
I really liked my Marquis 5500 which could power 220VAC welders and compressors. I think if I still had that capability, my enclosed trailer would look more like a shop than a garage. Only about half the mileage and third of the trips do we take the trailer along, so going with something that is still contained within the TC is better for us than a trailered powerplant.