Parametric planetary gear

I need to build a stackable planetary gear for a project of mine.

Little by little I'll complete this ;)

edit: you can find a video here
https://www.youtube.com/watch?v=CbXVSoI79gw
Sry, it's in italian.
The gear ration of each stage it's about 3.5 and 3.14, for a final ratio of 10.99:1