It seems to me that the only reason the R&A would look for a new course to add to the roster (not rota) would be if one of the current bunch chose not to host the championship or that some action by an outside agency, such as a blockade by French lorry drivers or a strike by signalmen, rendered a venue unsuitable - they do have plans for an alternative venue were some disaster to prevent the scheduled host being unable to hold the event.
As we've seen potential additions are few in number and mostly near an existing host. Royal St George's is the only host in the south of England, but if political pressure were brought to bear on the R&A to move the championship to other parts of the UK which have never yet hosted the Open, then the only way would be to rebuild an existing course, or even make a composite course out of two, as well as investing heavily in road and rail building, hotel and guest house building - a rather expensive operation even for the R&A. Perhaps there is a potential composite course from the 36 holes at Saunton, but roads and rails and accommodation are inadequate. Maybe something could be created at Pyle and Kenfig but the land is protected. Would somebody be given freedom to explore the dunes at Harlech - they're probably protected, too. You could make quite an interesting composite course out of the best holes at Conwy and North Wales - they are next door to each other in a manner of speaking - but you'd also have to build a vast bridge across the Conwy Estuary to link them. How about a composite course derived from Hillside and S and A? That only needs a railway bridge.
Only really revolutionary thinking - such as building a completely new course on land which at present doesn't seem to be links (if Kingsbarns can do it....) - will suffice. So, start identifying that tract of land now....