WRE would fit nicely in Disneyland if they replaced the current petting zoo/bbq area with that. They could even expand northwards in the backstage area if necessary as they did for toon town. Get rid of davy crocket canoes and make this ride it's replacement. That would give frontierland 3 great rides and make it feel bigger, which the western wilderness should feel like. Also, it could be differentiated from Grizzly rapids in DCA by making it more of a story like POTC, and less of a thrill/soaker ride.
Of course it probably wont happen, unfortunately this expansion area will be used for a franchise instead of following walts example.
As for WDW, simply move the train track north and west, build WRE adjacent to big thunder along the rivers of america. The current train track/bridge can be used for walking to that forest area where WRE could be. Seems like a no brainer to me.