How to make something like the Sims's CAS (create-a-sim)? Link below for those who have never played the sims

I want to make something like the sims’ create a sim. In the CAS, you can change the eye color, clothes, physical appearance, etc. I dont want to make 1000s of variations because it is very hard in the code, and i would have to change multiple things. Link here:
The sims CAS
This is all my info.

I will add a live demo

You can change use morph targets for different body types, like fat or slim, also different material color for skin color, different facial hairs using different textures