The first idea is the easiest. If you look at the shader mod that I posted that fades the character alpha based on distance you will see how to modify the alpha/transparency. Then this needs to be tweaked using SetShaderVariable instead of the distance calc - so one of the four floats that is passed from lua to the shader is used to modify the alpha. This will give you lua control of the transparency of any and all entities using that shader.
The second objective needs some engine updates too as you are targeting a specific entity within a batch all using same shader. I can’t really describe this further here. But you’re correct you can coerce it work like the editor does when you hover over an item. The shader variable is GlowIntensity if you want to experiment with it.
Cheers.