Alright, Girlinhat, need some advice here (or anyone else who knows modding well enough to answer this).
First off, thanks to everyone for the advice on getting them to survive worldgen in 31.25. Worked wonders. Although I'm still not in the cutebold camp (and leaning towards scaly, though not ugly and hideous), I still like the idea of kobolds as dwarven pets/companions.
I'm thinking of modding them to be pets, and trainable for war or hunting. How would I go about doing this, and what do you think would be a good pet value? Also, is there any way to do it and NOT have them show up as slaughter-allowed livestock? I'm not interested in kobold leather cloaks (though dwarves DO have cat and dog leather, so maybe it's not that out of the question).
Well cats and dogs aren't sentient like kobolds so it's pretty much just our culture treating most species as holy as Indians treat cows, but I digress.
Splint's description should work, but if you want a population of kobolds that isn't part of any civ and thus won't muss up that civ by modding them, try this:
Duplicate their RAW entry, renaming it kobold_02 or whatever. At that point you can add the [PET] and [TRAINABLE] tags anywhere in the entry.
You can then add [BIOME:NOT_FREEZING], [BIOME:MOUNTAIN], [FREQUENCY:10], [POPULATION_NUMBER:3:30] and [CLUSTER_NUMBER:3:30] to get them to show up in most wilderness settings besides bodies of water, tundras, and glaciers.
A good pet value may be 130. trained kobolds will then cost 130, and untrained 65, which isn't exactly expensive but still respectably valuable.
If you want them to show up with migrants or be purchasable from the embark screen/dwarven caravans rather than relying on elves or wild populations, you can add [COMMON_DOMESTIC]
They'll gain experience in skills, but won't be performing any labors unless you followed Splint's example and used DFhack.