Lets hope 5.5 helps more with this:
Yes Please !
and thanks for posting this
So I found a toon shader on Fab which essentially uses the engine’s distance field shadows system to effectively cast shadows onto unlit materials, so it’s definitely possible to do something like this without a custom shading model. The downside with this method though is that it seemingly doesn’t work with stationary/baked skylights, and it only works with deferred rendering.
https://www.fab.com/listings/dd792978-b257-407b-9416-43d7f421ad82
Definitely still need a way of accessing reflection and point/spot light data from inside of unlit materials though.