Bit late to the party, but will throw it out there for consideration. I did a bi-fold ramp for ours years ago for our two Pitbulls. Scissor steps are a nightmare for dogs and us. They are never level or solid under foot, so I'm surprised your still going with them. The ramp was just plywood construction. Hooked on the existing hanger that was just below the door. Deck was just under the width of the door so the ramp could be folded and slid in. Though could be built to not fold and still be slid in. Deck was carpeted and had 1/2" thick by 1" cleats like a boat plank, for extra fudge factor when wet. It was a first one to try and could have been made much lighter. Was even considering an Aluminum version with a bottom half that ext/retracted to compensate for varied height. But didn't get to the improved version as wasn't needed anymore.
The new NL we just ordered has a great set of stairs plus a nice removable third step.
I do like your rail idea. Be a good place to hang a small deck from. One that's light weight and could be stowed inside during travel. Maybe that with a set of solid steps going off the side would be a good option. Gives a half way down place to pause and readjust the kids, if needed. Have the deck hang so it's above your hitch so can still be used with the bar there. Side stairs also would work in that case.
Anyhow, I'm just babbling out random brain pharts......:p
