Unclean Beast Design(3.5)

[PersonMan]

I've decided to try and come up with usable stats for the Unclean Beast from the Demigod game. However, seeing as there are skill trees and the like, there could be several different versions. I've decided that the best thing to do is to make a modular design, with abilities "snapping in" or off. I'm not sure how I could do this, though, seeing as I'm not all too familiar with CRs, and want to be able to say "If this ability is equipped at level XYZ then the CR is increased by TUV".

Any ideas? Also, if you don't havy any idea what the Unclean Beast is, then check the wiki. (http://demigod.wikia.com/wiki/Unclean_Beast)

[Debihuman]

Since he's a "demigod" you should probably look at making this an epic creature if not an actual deity using the rules available in the SRD online or in Deities and Demigods.

Debby