In WGE, it's implemented so that the Special Unit (SU) is only available when the racial skill is leveled up to 4 (as a level 4 racial perk), which requires a Pendant, but it doesn't have any other specific requirements for leveling up, except for the racial skill tree. So, essentially, the SU can be used in various builds. I can suggest this approach.
I've been dreaming about this for a long time.
Is there anywhere I can download such a mod (specifically for the skill wheel)? Or can someone tell me how I can create it myself? :o