Personally, I'd balance the LA with extra "racial" HD, and force them to take racial HD as half their Gestalt until they run out.
For Hobgoblins, I'd force them to take 3 levels of Monstrous Humanoid (full BAB, d8 HD, 2 sp/level), and I'd spread out the ability increases over 3 levels (+1 Wis/+1 Dex each at 2nd and 3rd level).
However, that's just me, and I hate Level Adjustment.
-- N