If that tweeter absolutely is for you, I would give B&W a try. If you don't ask, your answer already is "NO". You are correct, they may be unwilling to sell the parts to a person who does not own their speakers(and can provide them with a serial number and/or receipt). I would say that it is probably difficult to match that tweeter exactly in the ultra high end driver lines. The Nautilus is a metal dome, and will have certain characteristics/sound that most expensive tweeters of today(soft domes/Ti02/kevlar/ceramic/carbon) do not. Most metal dome tweeters have a harshness avoided by tweeters like the Morel soft dome you mentioned. Spend some time listening, you may find you like one tweeter over another. Then, you can have what you truly like the best.