I think the difficulty in replacing or even inspecting the air filter element is more a function of what the body builder has done rather than the chassis manufacturer. We have a 2013 Adventurer on the Ford chassis. I've checked the air filter a couple times. In both cases it took less than 10 minutes to open the box, remove the element, inspect it, and reinstall it.
Here's a link to the Ford Brochure for the F53 chassis.
http://www.fleet.ford.com/resources/ford/general/pdf/brochures/2014/Class_A_brochure-2014_LoRes.pdfThe air filter box is hanging out in open air. There should be no problem removing the element unless someone builds the body so close to it you can't open it.
The procedure I use is:
1. Flip open the 3 over center latches
2. Loosen the clamp on the air intake tube
3. Push the top of the box slightly to the rear and lift on the front edge
4. Pull the top forward to release the tangs on the rear edge from the bottom of the box.
The cover cannot be completely removed unless you disconnect the wire to the sensor.