Love the practical explanation of how straightforward it should be. Especially with the finite set. Hell, they could send an email to all 22,000 saying "We're sorry, we have to raise your renewal fees by $12 a year. We hate to do this, but we're having to do a lot of extra work to support this unique type of domain." they'd bring in $264,000 a year, surely that should be enough to pay a single skilled developer to manage this and also be available to help smooth over any future complications.