Ok the day started bad, the algorithm i've spend 2 evenings working on is simply to heavy for flash. But i was walking for a few days with a litle idea behind my head.
For the bitmapdata only renderers, i've wrote a very fast (who am i to say so, just see by yourself!) lightning code, very simple code, but very efficient. So i decide to apply it to the bitmapMaterial, the same classes as in Papervision.
After the defeat of the shading, i could balance with a very fast flat shading.
If there is sufficient triangles, you even could get a smooth fx illusion.
According to my tests on my G4 and G5 witch are not speed monsters anymore, i could set up good FPS on every models i was loading, in some cases i couldn't say the lightning was slowing the process of rendering down.
My job will be now to add to all materials this flat light option, a lock light option witch will also assure that normals will be calculated only once, so the light will not be calculated on each iteration. Handy if you want to light that chair with no function behind that table in the back of your scenery... the model will have lighting, but after 1 refresh, the light will be just dead!