I would think if they are going the cheap route, why not overlay Rockin Roller Coaster with Guardians, update GMR with new show scenes and use the expansion pad off Sunset with the Mickey Ride? Seems like a win win win in my book.
With Energy, I feel they could come up with thousands of Original CREATIVE ideas for that space that would still tie to the Epcot Mantra.
THIS! I guess it just makes too much sense for today's Disney (in addition to not being the cheapest possible option of course).