The workflow seems intresting:

so basically,

create your level in Max,

export the models into a folder using your plugin,

export your level into WED.

Then, take your folder containing the duplicate models with different uv sets, load em into your python program, and it'll combine them.

Then in your action for every entity, have it reload the entity as the new combined mesh? Will import_mesh() read the file name of the model and do this last part automatically, or will we have to type in the mesh name for every instance of this function? Hopefully it's not the latter, cause then you'd have to create different actions or skills for every entity.