Becoming the goblin leader would be terrible to implement in the narrative though because you would have a small army at your command.
I don't think it has to be overly complicated. Just being acknowledged by the goblins and them not becoming hostile towards would be enough, I think. You've already done the raid on the Grove with them, thus fulfilling their main purpose in the game. They could either bring them back in an upcoming battle towards the endgame, if there is one planned. Otherwise, I think a couple of sentences in the Epilogue (similar DA:O or DOS2) would suffice.
