I tried to implement this for FP7, but it was more problematic than expected.
3DS Max uses explicit normals only for viewport models, and requires a specific mesh class to store them. Unfortunately Forest 7 uses a different class to store the geometry, so we should rewrite several parts of the core to support it.
It's doable, and the issue continues in our to-do list. But it requires a lot of code rewrite and testing (to be sure we don't break anything in the process). I hope it can be done for next versions.