A simple, if far from ideal, solution could be to just add elves and goblins (or whatever you want) as additional castes to your dwarf creature file. That doesn't require any kind of DFHack stuff and the elves and goblins will behave as full fort members because as far as the game cares they are dwarves.
This has some major drawbacks. Since the game thinks they're dwarves, they'll marry in with the dwarves. I think the new orientation tags will let you prevent this by setting the romance and marriage probabilities to 0 for the interspecies mixing, but I haven't tried it and am not sure. It might have only supported genders, not full castes. The other drawback is that they'll randomly select a caste when giving birth, regardless of who the parents are. So, yes, two dwarves can have a goblin baby, or a dwarf married to an elf can give birth to a goblin, and so on. There's nothing you can do to prevent that, although if you were using DFHack you could later change the baby's caste to something sensible, but that wouldn't prevent it from happening during worldgen.
If you were using DFHack you could probably find better ways to do this than weird caste stuff though. DFHack does now work with the newest version of the game I believe, but the old scripts will almost certainly require fixing.