I think RnRC would be a fine spot for Guardians. Better than ToT obviously, and better than in the UoE pavilion in Futureworld, though a lot would depend on an edutainment tie in for that spot. On the other hand, if we are talking RnRC you are talking about doing it now, and shutting yet another DHS attraction at a time when options in that park are paltry at best, or you have to wait several years after SWE opens. Pushing it out into the mid 2020s perhaps. That is a long horizon.
I think it is a rock and hard place for RnRC right now and it just needs to hold out the way it is for a decade. If you remember that Disney hadn't even purchased Marvel or Star Wars 10 years ago, a lot of different options could appear and disappear for an overlay on one of my favorite rides by the time it is feasible to rework it.