It would break the story because even if you decide to RP as a non-absolute worshiping goblin, pretty much every NPC you'd meet in the early map would try to kill you on sight.
Yep, like that scripted combat at the Druid gate, where NPC's are yelled at for leading the goblins to the Druid camp. How are they going to feel about the player's own party including a goblin?
And how do you bring a goblin into a city like Baldur's Gate, which is hinted as a location to visit? Larian already used the "magic disguise" theme for one character in DoS2. It didn't really add anything to the game, and would feel very forced here just to include that one race.
