I always found getting the stuff out of the kitchen (where it was staged) down the stairs and out to the driveway was a lot more than hoisting it through the door of the RV.
While my wife still lived, I hauled the stuff to the door, set it on the floor of the RV, she took it from there to put it away. Now she is gone, I do both jobs, but it is half as much stuff.
If the front passenger seat suggests itself as a problem, you might look for a mid-door coach, preferably door leading into the kitchen, which is where most of the stuff goes.
With the total amount of carrying involved, I think a conveyor at the door would address a relatively small part of all the work involved. If the door and steps will be a stumbling block, you might look at the bigger picture to assess whether or not you are physically up to the work involved loading for a RV trip.