This concept is used commercially where required by law and is known as a "C Train Dolly".
"The 'C-Train' is similar to an A-Train except that two drawbars are used to eliminate the freedom to rotate about a vertical axis at the hitch point. The dolly is equipped with a self centering, self steering axle that requires a side force of about 0.3g to steer. Canadian regulations allow slightly higher loads on C-Trains than A-Trains."
mty40.htm, DOUBLES: A-Train, B-Train, C-Train; Tractor towing two Trailers
Some of these dollys have a steering axle and some are solid. (depends on the length of the drawbars, the application, and the jurisdiction rules.)
The "C Train" was an attempt to eliminate one vertical pivot point on a multi trailer application thus making it somewhat more stable. Many "A Trains" were converted to "C Trains" to take advantage of the more generous GCVW's allowed.
There should be no reason that this concept would not work on a RV application, IF THE TOW UNIT HAD SUFFICIENT FRAME ABILITY TO HANDLE THE STRESS.
I doubt any pickup or 3/4 ton equipped from the factory would qualify. The distance between the drive axle and the hitch dolly would be an excessive ratio verses the weight of the towing vehicle.