Not because of navmesh really but rather because if there is a navmesh-based tool to convert BSP into RBN files, I'm afraid that the RBN nodes will not be a natural path... Kind of going only around meridians, no short cut, not taking cover for the path, ...

Actually, the RBN nodes could be made human at the expense of putting enough AI in the code ;-)

Anyway, AFAIK there is yet no such utilities BSP -> RBN...

-eric