Make changes that allow set matte to work the same in precomps with continuous rasterization.
When designing for animation you often need to use the set matte, but that means no precomping unless you toggle Continually Rasterize off, which means vectors are no longer vectors and no longer scalable without losing quality.
I don't understand why AE is made in such a way that a precomp completely changes how the set matte effect works. If I'm designing an animated character and I use the set matte to allow the pupils to be hidden by eyelids etc, then it should look exactly the same in the precomp layer. Much needed change.