Possible to refresh textures between render layers?

I want to render a renderlayer and then use it’s output as an image texture in a material in another render layer.

It is possible to have an image automatically save out to a certain path, and for that path to match the location of an image texture within a material. I know there are scripts/addons that refresh textures. But I do not know if the image is actually saved when the renderlayer finishes, or not until after all renderlayers finish. Can anyone shed some light on the order of operations here?

As an alternate solution, it seems it should be possible to write a script that renders just layer 1, then refreshes textures, then renders just layer 2. I believe this is already possible manually. Is there a caveat that would make this not work?

Hard mode: I want to render a render layer, run it through a certain compositor stack, output it, put that image into a material on another layer, render it, then run that through it’s own compositor stack, but also still have data from the first render layer to use. Possible?

Thank you.