Franks explanation of the goal of this hole thing is very good!
This plugin would make things a lot easier!

Here is another example how the plugin will be used or what it can do:


the light-mapped scene in the second screenshot is achieved by creating a second model with the lightmap UV coordinates and the lightmap texture, placing it in the excact location of the texture model and using a shader to blend both models together... it is awfully complicated and any game programmer will kill you the for doing this in the same way this method kills the performance!

With the plugin it will simply be: one model with 2 uv maps + texture + light map.

concerning the approach of actually saving the second UV map my idea is the same as Wichts:
You have a second copy of the model imported to MED which uses the Lightmap-UVs and you use the export function to export the UV coords to a file! now you can use the plugin to append this second set of UV coordinates to the first model.

I think ventilators idea is not that bad!
The models with lightmaps would most likely be used to replace level geometry, therefore the models won't need to have animations or bones! A own model format therefore only has to include mesh and UV coordinates, skins can be loaded from external sources!

I would make it an even 250 Euros!
Ventilator, willing to give it a try?