We agree that it’s not a tenable solution.
Again, I think the best we can do at this point is move to more complex alphanumeric SSNs.
Just making it a hexadecimal number would increase space available for assignment. You can't make the number much larger though, as we know that it is difficult for folks to remember more than 7 digits. That's why the number is typically broken up the way it is. It makes it much easier to remember in chunks (yeah there are other reasons as well). Nine is actually pushing the limits of what the average person can easily deal with. I would really like to see it expanded to a 10 digit hex number anyway, with the last 'number' being a binary check bit. That would give us 68,719,476,735 plus a check bit. That should be enough for a while.