For textures resolution think of how many pixels the head of your figure will be in your final render, and how much you will see of any body or limbs texture in a figure that is fully dressed. I do not mention eyes. I do not mention specular, bump etc. maps.

There is a lot that can be done to free up space and speed up.

Makes me think of a script that does just that: swap textures to a size that makes sense for the project at hand. Problem is that Python access to the texturemaps cache is limited to zero.