Rengineer
'Forgive me for asking something here that I've been wondering for some time. Why isn't the Typhoon qualified to fire the Brimstone (yet)? It'd seem like a logical thing to do I'd think.'
Put simply - cost. If you've got GR4s to fire the DMS Brimstone (and Stormshadow, 27mm, Pwy2/3/4, etc) then why spend good money this year get your (primary role AD) Typhoons able to duplicate? GR4s will go eventually and just before then you need multi-role Typhoon.
Given 20/20 hindsight you could argue that it would give you cover for Libya, but that's a bit harsh!