Limbs now store their own dna/species info. This allows transplanted limbs show up as they are, instead of conforming to mob. Vox-cat-monkey hybrids, rainbow skrells, go wild.
Also changed rejection to cause infection instead of straight up organ damage - wouldn't want your newly acquired catpaws fracture out of blue.
As a bonus, attacks are tracked per limb, so for example having kitty claws will give you the corresponding attack