Not a lot is my particular verdict, they should be a fast multiplying and needlessly violent race like they are now, kobolds with live births but more aggressive and armed with pointy sticks and a fondness for troll herding and stamping all over slaves and people lesser than them. Fond of long range weapons, and lightweight exotic stabbing sticks to be more "masterworky", not terribly well armed but well manned.
Goblins domestically have anger issues and punch each other and everything else in sight frequently so that ought to come into play with promoting martial skill or some way to use or blow off that anger on a target other than the rather surly troll inkeeper who swipes their head off in one punch.
Trolls themselves are slow learners and part harvestable livestock/second class citizens who can claim rooms, if actual goblins aren't interesting, you could refocus on trolls and other such laborious races created through the slave system and spawning friendly slow learners for different functions and defense application unique or not. Import from slavers or just put down a 'troll heap' made out of refuse as a workshop and a convenient way to dispose of bodies/rubbish that accumulates in exchange for trolls, tribute trinkets and the like paid by passing wild trolls (applying a little imagination) feasting away on your junk.
Literally cash 4 corpses, to which there will be many. I guess using slaves sacrifically aswell would be helpful, pushing them in literally as fuel for a furnace when they run out of logs to burn, and making them suffer by teleport spawning them inside cages for display, given that goblins have sick desires to see people in cages (i know firsthand from goblin fortresses). Or even more amusingly getting slaves in cages, then releasing them on mass to make more bodies to get more trolls and combat experience.