To be honest what other shouts can they add?
Actually, aside from the shouts used by Alduin, there are shouts we don't have access to that the Greybeards use. Like their shout that summons a spectral copy (when training you for Unrelenting Force), or their shout that opens stuff (when teaching you Whirlwind Sprint).
Well, REL_Dovahkiin ninja'd me here XD
Aside from that, with the size of the team needed to make Skyrim, I'm sure a variety of ideas we don't know about are still floating in their conference room(s)