What a sweet idea! I have tried it with my all of Europe N3590lmt and it worked brilliantly so no more Express drama's for me.
All I need now is like minded member who has LMT for North America on a compatible Nuvi, 3490, 3590, 3597 and who wants all of Europe maps. PM me so we could discuss an exchange of .xml files.
If you think there are problems with this idea please explain.