From the documentation (3draft2 p.6-43) it would appear that if I was making a 3D model with just a base map and bump map I could use layer 0 for base and layer 1 for bump map. If I was to then add a night map I would have to move the bump map layer to layer 2, is this correct?

Also am I correct in assuming that given the notes from the 2008 user group and the addition of many more types of texture (e.g. gloss ,height) the system of layer assignation will have to be revised so that the correct mapping can be made from layers to textures?

Yes, you are right that the assignment of textures is based on the layers assignment for your textures. You are also right that the CDB 3.1 draft will contain more texture types and that it could require re-assignment for a user to include these new texture types. We are also defining the proper assignment for the existing and new texture types.

Could I have some clarification on how texture layers in openflight would be mapped to specific texture layers in CDB?

I.e. how would we take the diffuse map and dirt map for an apache (both with different UV co-ords on seperate layers) and set them up in CDB?