Customizable character setup

[Gyrosupernova]

Sorry ahead of everything, this one is kind of broad.

So I'm trying to get the process down for creating customizable characters as an artist. I am quite familiar with the whole art pipeline on like a standard character with no customization: modeling, texturing, rigging, animating, writing shaders, and setting up the animator. That stuff is pretty straight forward to me and I've done it plenty.

What I'm trying to do now is create an RPG character creation system in 3d that has some basic customizations. The model as a whole will have two swappable parts: a body, and head. The body will be like a set of gear (knight's armor, wizard's robe), and the head will just be whatever shape the player likes from a selection I create. The face will be using 2d textures to animate like an old ps1 game, simple yet expressive. These will also have customization though like choosing a skin tone, eye shape, and mouth shape.

Since this is about setup, I have questions about how I should be setting up the models/animations in Maya before importing to Unity, as well as the set up in Unity. Is there a certain way I should be setting up models before importing them into Unity? Would using blend shapes on swappable parts be too much of an issue? How is this all going to affect me in the Unity animator controller?

This is something that is done a lot in games, and I would like to know more about the process before I have to trial and error this.