Google actually already has a system to automatically detect and filter incoming nude pictures. It allows apps to blur then and you can then opt to view them. It's a separate application and uses locally running machine learning.
I can't remember the name of it and if it's just on Pixels, nor what applications it works with. Might just be for their own messaging apps or it might be more deeply integrated. If anyone is curious I'll try to look it up after work.
The point is they already have something similar to this they could maybe leverage.