the airlines could (collectively) stamp this out with minimal effort

if for example a UA customer wants to status match onto DL, the DL application could capture two or three non-identifying pieces of information and submit it to UA, for example:
1. MP number
2. Status level
3. Name one flight UA taken in the last year

then the UA system would respond with either "confirmed" or "not recognized". Subsequently, you could only sell a status match to a maximum of one person per airline because after that the system would recognize you as a duplicate