This is one of those ideas which sounds simple, but is deceptively complex.
What is meant by "unique dialogues"? Just an acknowledgement of "Hello fellow goblin. Goodbye." or something unique to each goblin? Should named goblins get unique dialogue and unnamed goblins get generic? Should goblins question whether this strange new goblin is part of the camp or not. What about reactions the goblins have to things your disguised character does? And did we forget to mention that all of this needs voice acting?
The amount of things to take into consideration could spiral out of control.
I understand there would be a lot involved, I'm not looking to see it implemented in EA, more of a long term final product thought. I assume they are still working on dialogue and quest branches for gnome, half-orc, and other races as well as classes so the throughput of work could be streamlined if goblin stuff is worked in while that's happening.
That being said, I don't think my one suggestion will change their course of action. I feel there may be a good chance they already have this in mind. And if they don't, then it won't happen. No biggie.