Mike,
Depending on the green, removing it is not necessarily easy. It all depends on the green site, if there is no bunkering and the green blends into the surrounds then it should be easy as there is no earthwork involved, however if there is then there are the issues of protecting the contours, adding/grading/removing soil etc. Depending on fairway grass type the rough around the green may have to be removed and resodded/seeded/plugged to match the existing fairway and then the opposite of course to return the green complex.
I guess if you're hypothetically;) thinking of removing a green with the intention to potentially reestablish it later then some extra maintenance (cultural practices) on that area probably wouldn't go astray such as aerating and topdressing etc it with the other greens, to ensure it drains etc consistently with the others when it is reopened.
My original post would still work in any situation but I was thinking more about one that was 'lost' many years ago, if you have the advantage of being the one removing it, for the small extra maintenance cost each year why not make the best of it to ensure it can be as close to the others if it returned.