Coochy,
the post-82 thinking on having a runway closer to the FI was about supporting a fleet with AEW and ASW in the unlikely event of an exact re-match.
the more recent thinking is primarily about developing the local island economies - that and the cronic lack of tanking assets available to bring down reinforcements. diversion airfields are also an issue - apparently no one particularly fancies the prospect of a C-17 with a Parachute Coy on board or an F-35 or Typhoon having to divert to a Lat Am airfield because MPA is closed...
Stanley's runway is less than 1000m - it could be extended, but not by that much, and if the weather closes MPA, it will probably close Stanley as well.