Has potential!
Walls need to be covered by observation and fire, and that costs money that nobody wants to spend.
If citizenship/residency were an alienable property right, though, I think many haters would self-deport to sprouting Third World "Jonestowns" in a tantrum or out of a desire for free $.
Only the rich ones leave. Why would you leave the source of your UBI?
You overestimate their ability to:
(a) math
(b) delay gratification
I promise you, if Australians could sell their citizenship in a free(ish) market, we'd see turnover of at least a million a year.