Nanomage, I dl'd DFusion, and it has a util called "Friendship" which loads a race list and makes them able to work. Tigermen are already included in the default list btw.
I played around quite a bit with the tags like you did, but was never able to get the game to recognize any non-dwarf as proper labour.
I'm playing with the defs for the Dwarf race tonight, for my "Dwarven Slavery" mod idea, made Castes for Male_slave and Female_slave. I made no changes to the civilization entity. The new castes are untermensch, pack animals/wagon pullers/pets, hunting/war trainable, and the other dwarves will butcher, tan, cook and eat them
. They can be ordered and bought in cages. I also gave those castes a mountain biome, so possibly getting wild mountain dwarves you can capture. And with all the dwarf tallow and dwarf leather around, I'm sure dwarf soap and dwarfskin trousers are just around the corner. There were some dwarf leather clothes among my starting gear.
They do befriend, marry, have kids with the other dwarves though, so they or your "real" dwarves can tantrum if they get butchered. In testing tonight, I had 2 of my starting 7 go insane within the first year due to this. This relects Stockholm / Lima Syndrome in real life, so it's actually pretty realistic. Basically not every dwarf can deal with running a dwarf-butchery operation.
Unfortunately, it's still all a bit too buggy and weird for popular consumption. Ghosts are being spawned with no name - just "Ghost", even from the normal dwarves. Children are born to parents normally, but the child's thoughts say "He is the child of He" as the parentage. And the kids inherit the mother's (tame) tag, even though I'm pretty sure the children are being spawned with the default Male/Female castes (I gave the new castes a really low POP_RATIO). So, Dwarven law on this matter is of limited slavery. You may be a slave but your children are free-born (but still "marked" as to their mother's slave-status).