Take a look at where I'm going with this and let me what you think. It is basically a heavily modified Babylon Unity Exporter
Demo Video Link
U3D - BabylonJS Game Editor Toolkit Quick Intro
Demo API Update
Warning: I tried to make it shorter, i took a deep breath and spoke as fast I could but it still took about 1 hour and 20 minutes. But the technical folks who are up to it and want to see how to use and how i put together a Manage Scene Component API with a light wei
thank you @MackeyK24 it's better with my single directional light in mixed.
I have tested with Coordinates Index 0 and 1, but the result is very different than the unity lightmapping.
If you want you can test with this free scene : https://www.assetstore.unity3d.com/en/#!/content/65679
I have fixed a bug in the exporter to export this scene : https://github.com/BabylonJS/Babylon.js/pull/1618
thx,
Jeremie.