Obviously it's the suddenness of the transition more than the actual steepness of the driveway that's the main problem. If you can make the transition at an oblique angle, that can help...but very frequently that is not possible with a driveway.
I would not really recommend the skid wheels. Many travel trailer (and other RV) frames are not designed to support the full weight of the RV from the extreme end. Besides, to be effective, the wheels need to hang below the RV, and cut down on the departure angle even further.