This is a late response. We ordered in October, it arrived about 4 weeks ago, and I'm trying to set up installation for a rear air conditioning unit. The only one that seems accessible is a Webasto product, and I was told that the company doesn't use the provided connections for DC or for the compressor. So, I'm not sure what the benefit is, after adding the option.
Others have said that the dash air is very good in these vans, but ours is new, and at 80F, with half of the insulation installed (still working on it), it was a sweat box. I took it to the dealer and they found a resistor that wasn't working properly. The tint in the windshield, driver's door, passenger door and rear doors doesn't do much to reduce heat, so we will also be installing Rayco film.