You have posed a difficult one here.
As already said, with your fabrication skills someone like you is definitely needed to sort out the many NLA listed parts or alternatively have the know how to replace with similar from other vehicles. Your knowledge base would go a long way.
The question is how many people would be prepared to pay for fabrication?
If you don't get the custom, you can't pay your bills. If you widen your customer base, you will not have the time to do the fabrication work.
Another member on here recently started a car meet in Silverstone. Slight lack of Audi member support led him to open up the meeting to any car over 20 years old. Perhaps that is a thought?
Not much in the way of helping with your quandary I know. But I for one, would sure be glad to know there is a specialist should i need one.