I have never come close to something like this in Firefly - impossible.

Render time was 3 hours 4 minutes.

I think it's really great that it's finally possible to do stuff that firefly simply can't do, and to easily do stuff that firefly could only fake by means of very complex node setups.
But... 3 hours is... glacially slow for that render.

Here's a rough facsimile of that scene rendered with Twilight, a plugin for sketchup - I stopped it after 11 minutes.