A mod for Oblivion adding the centaurus race to the game has been created some time ago. Follow the link below to find it -
http://tesalliance.org/forums/index.php?/files/file/775-the-oblivion-centaur-project/
The project was freezed after the release of alpha version. The race had many defects, for example, after the hero was attacked with paralysis the character model parted in two pieces, and also animation was poor and there were lots of other flaws. Though it was nothing in comparison to the articulation of the upper and lower parts of the body. Slips and fractures in the model made it impossible to enjoy playing at all. In order to prevent players from seeing this mess I tried to create armor for the lower body with the "collar" masking the joint. I used the "Dark Illusion" set of armor made by SkeletonK, patched the hole in the shoulder and replaced textures.
I also shaped the outfit for the horse body and its fore legs in the same style. Initially the whole armor was fused with a horse body, but now it can be removed fully or partially. The effects of enchantments and bonuses to defence work correctly. During the experiments the elven, mythril and imperial legion armors were successfully adapted.
It is certainly possible that the other sets will be adapted to allow playing by the centaurus race without annoyance.