I asked this in the [main LWRP thread]( Feedback Wanted: Lightweight Render Pipeline page-5#post-3981121) as well, I imagine the current solution is exactly that: use emission channel or build custom lighting from ground up with unlit base, otherwise it will involve changing core shaders.
(ShaderGraph_ExampleLibrary repo might give you some nice idea to kick start custom lighting, depending on your use case)