Having lived in two class A rigs over the last 14 years, I would say that you should look at a toy hauler for a workable shop. That is IF you plan on using it a lot for projects.
I'm happy with my dinner table working as my benchtop most of the time when I have an electronics project. All my parts bins are in the space behind the bedroom TV, plus under the bed, so it's easier to work inside when I need to grab a part. Not always though.
I once rented a 1 room cabin at a RV park in addition to my RV space in order to work on a complicated project so that's how crowded working in a class A can be. Obviously, it's kind of a hassle working on a project inside the RV for any length of time.
When I do wood working or metal working, I use picnic tables along with my clamping vise like another poster said.