Generally any unittype that has this <SkeletonPath>Gfx\HKB\Units\K_Male_Skeleton_01.hkb</SkeletonPath> can be turned into a champion safely with a few modifications. Other than that, you'll run into a lot of problems with equipment, graphics and animations. Stormworld solved this by making a lot of stuff half-human, like the Centaurs and the Drota.
There is another option though, which is to not turn the bone ogre into a "real" champion but still give it traits when it levels up (like the Sion).