Had one of these in a Bounder, no slide tray. at around 5000 hrs I pulled it (dropped it out the bottom!) The only modification I made was to cut out a hole, 12x12 or so in rear panel, then got a piece of diamond plate aluminum to cover the hole, installed with nut-serts, so I could change belt if necessary in the future, without dropping entire set. Of course I did full P.M. maintenance while out, including belt, hoses, coolant sensor, water pump and thermostat, valve adj., etc, etc.
The commercial units do have a service door, but I doubt that it would help with the gen stuffed up in the RV . They can be very useful if gen slides out, gives good access to fuel filter and oil filter. The commercial units are identical to RV units, with the exception of having a 12v battery charging system installed.
I do work on these gennys for a living, and usually will always change the belt and water temp sensor, every time I have a unit out of the coach for whatever reason.