No, you work with many of the Mechagnomes in their resistance against the ruler, King Mechagon. The prince is the one leading the rebellion. The rebellion is also a rep. That's how you do the quests on Mechagon, with Goblins showing up as well.
It's a fair assumption that Mechagnomes are going to be playable, due to their
player character customization and
a unique female Mechagnome dance animation, which are generally more for player races. They also have a rep, which fits in well with all other Allied Races.
On topic: Sure the Alliance has had a bit more boring Allied Races. However, the Alliance, as a whole, is a bit more boring of a faction. Getting Vrykul wouldn't change much of the problem - they're another shape and size of human, exactly like the Kul Tirans, for instance. They haven't really set up many other unique/interesting races that are 100% Alliance. though, I do feel that Lightforged should have been customization for regular Draenei, and the Broken could have been the Draenei Allied Race. However, I'm content with everything else so far.