With all due respect, I don't think you understand their program. If you work your relationship correctly with them, you can generate a lot of business from them. I speak from personal experience. I try not to go more than about half an hour away, unless I can justify it say by visiting a friend. And the signings (presuming they are WaMu HELOCs) only take about half an hour.
Yes, they will most likely find someone else to handle the specific signing you mentioned, but so what? You should keep in mind that that person who accepts it may be much closer to the signing location. And you may get another request from them for that time slot that is more geographically desireable. That has been my experience too.
You should also be pleased that they have accorded you a broad coverage area. If a notary screws up a lot, MD will cut down their coverage area. Or so they say.