I would prefer a different system.
A sort of 3rd faction that is really just a bunch of mercenary races that are typically 'enemies'.
Satyr, Harpies, Furbolgs, Ogres, Murlocs, Naga, etc
They would not be a unified faction themselves but would just start out as either Neutral or Unfriendly with both the Alliance and Horde and would have access to quests from both factions.
Or something like that.