I have both and I do not think that would work. They use the same holes, and the rock rails are beefier then they seem once you get them off the vehicle. So I am going to go with this is a no-go. It is one or the other and OEM rock rails and OEM side steps will not play nicely together on the same side of the same bronco.
That being said, I do have the OEM side step on my passenger side, and the OEM rock rail installed on the driver side of my non-sas Badlands. LOL. I bought the steps for the wife but did not care for them for myself (I am 6'6" so don't need the help getting in), so I took the step back off the driver's side and reinstalled the rock rail. Kinda tough to see both sides at the same time, so no one notices that the sides are different.