For the past six months or so I've been working on a high-performance proprietary offline renderer that I plan to release as a standard product and as a plugin for Amethyst, Blender and Houdini, both to render standalone scenes and as a lightmap/AO/etc. baking tool.
If you'd like to check out the project, I've created a public README document here: https://github.com/raygon-renderer/readme
with links to our Discord server and ways of supporting the project.
It's still a ways off, but things are coming together quite fast now.
Example from a week ago:
If you have any questions, don't hesitate the ask!