lift kit is your better option if you just gotta, a moderate lift of a few inches is easily done and not very expensive ( there are threads- and also look at this:
stock, the clearance is low and there are many, many components inboard of the skirts which are same height- tanks, piping, generator
generally the side skirts are at the same level as the tanks under the floor- most class b's are built as genteel highway cruisers.
my 2006 pleaure-way on a chev is about 8" clearance
the RT 190 and 210 models offer alot more interior space than the 170- longer wheelbase, but with that would come a higher likely hood of high centering.
the 170 on a chev is more likely to have the 4.8 liter vs the 6.0 on the larger models
some 4x4's are coming on the market, but look to be aimed at the suburban mom who is worried about 1/2" on snow on the driveway
you may want to look at sportsmobile, there are also other converters who will build what you want but the budget will soon be over $100k and climbing
my neighbor has a self- conversion of a 99 Ford Pleasure way excel model- his 99 ford sportsmobile 4x4 burned down in the driveway- so he swapped the running gear into the PW, I just walked by and my eyball says he has about 13" clearance at the lowest point ( dump drains).
he uses it more in Baja- it isn;t great on teh highway- the high center of gravity on a 9000# van makes it squirrely as can the wind load
in my neighborhood alot of the baja and offroad guys use lifted trailer trailers or a lifted pop up trailer- these are bult pretty lightweight but can still carry dirt bikes or atv's- and use a bike truck to pull them