Why not fuck both sides!!!
IMHO as long as the BE don't lose the Isles of Queldanas, is ok.
Also that may push the BE to attack the Exodar and reclaim that island in the name of the Horde.
Note: Also an invasion of Silvermoon does not need to end with the Horde losing Silvermoon, instead only lose Queldanas -not the isle but the zone around the city-, how? In one of the Chronicles its mention how Silvermoon was elevated to the skies once (Dalaran style), so that its a plausible option too
Note 2: This would basically just make Silvermoon move to where the Exodar is (maybe in Bloodmist island instead) and have the Exodar where Silvermoon is.