I also can not confirm a problem with stencil shadows on shader surfaces. I'd need to have a look at that shader.

Stencil shadows already react on dynamic lights - see manual. And models do already have a second UV coordinate set.

Only your wish that shadows should become more transparent in the distance can not be fulfilled with stencil shadows - at least I wouldn't know how to do that. A stencil shadow is 2D and does not carry depth information.

We plan to add a smooth shadow shader to the MtlFX shader library, as an alternative to stencil shadows.