Still agree with rsm2000e and theshack440. Here in the US, I've never seen the rear stairs used, and an option to disable it (either globally or regionally) would be nice.
Umberto does have a point that would look strange otherwise, though. With FSX doors opening both forward and aft right doors at once, it would be strange to have one door just open. I'm not sure what's the deal for water/lavatory services, though, as (from what I understand) they typically have ports on the exterior for the "blue juice" and potable water. Galley services are taken care of by catering and cabin cleaning by the ground crew (meaning at the gate, not literally on the tarmac).