Thanks.
I have begun making my own creatures. The first one is ready, called Bhederin. For those who doesn't recognize the name, I was inspired by the Malazan Book of The Fallen, created by Steven Erikson.
The best description of bhederin is creature resembling cattle, they can usually be found in savanna or grassland. Those can be captured and tamed, providing good source of meat.
I used the cow as basic template, modifying several parts. I changed the population size to 20/50 and removed the MULTIPLE_LITTER_RARE tag, which should refer to the huge packs described in the books. I also gave them bigger size, as they are described as huge creatures. I also removed the ability to milk them. I also made the males quite aggressive, giving them LIKES_FIGHTING tag.
Now, I made some testing in arena mode, and the bhederin seems to work perfectly (no problems in creature templates, graphics nor anything else I was able to determine). First I put one bhederin bull against black bear. Bhederin won. Next I created male dwarf, equipped in iron axe and iron shield, to fight against the same bhederin. Again the bhederin won, disarming the dwarf by smashing his spine with kick. Next I created a dwarf equipped in full iron, and again pitted against the same bhederin. Bhederin won.
So, you should be well prepared if you are going to hunt these creatures down, which is quite good idea for the meat those produce. Just note that they can be very dangerous.
EDIT: I pitted one bhederin bull against dwarf equipped on steel equipment (normal shield and axe, not blessed versions) and the bhederin won, though the battle took quite long. There was over 150 pages of reports, last 100 pages or so were how the bhederin systematically broke every bone of the dwarf before killing it.
Next I pitted fresh bhederin bull against dwarf with steel equipment, with blessed shield and axe. This time the dwarf won the battle, though just barely. In fortress mode I believe the dwarf wouldn't have survived to hospital.