Some new official info from ubi forums

[Avimimus]

Originally Posted by The Kraken

The weathering will also have a specular map (where the underlying metal is exposed), which may not be available to "normal" skinning. So this approach wouldn't provide the same options and quality as the built-in weathering system.

But, if the plans for an SDK hold up, we should see entire new aircraft created (which requires this level of access).