Perhaps an AN124 or DC10 or even some old airliner from the bone yard would be a more appropriate gate guard as there are generally more clapped out civil airliners on charter to the MOD at Brize these days than RAF aircraft if you discount the 216 static display Sqn Tri-motors, that spend more time U/S than flying.
The way ahead is to ditch the strategic AT fleet and moved all passengers by charter like the worlds largest Air Force does.