I would be very OK with all of this.
Maybe change it to exactly 1/8 sizes, for consistency.
- horse cock = 1/8 = human
- tail + ears = 2/8 = halfkin
- tail + ear + horse cock = 3/8 = halfkin
- tails + ears + fur + horn = 4/8 = beastkin
- 1. Skin (scales, fur, goo, ...)
- 2. Tail.
- 3. Ears.
- 4. Other (horn, wings, animal genitalia).
- 5. legs. (digigrade, pantigrade, testicles, snake tail, ...)
- 6. Arms. (claws, paws, ...)
- 7. Torso.
- 8. Face (Muzzle. fangs, long head, ...)
System isn't perfect because for some races the only physical difference is pointy ears (elves) or wings (seraph) or whatever.