Anyway, couldn't you isolate those who have just been immunized for a couple of days (that needn't mean keeping them in hospitals, you could order them to drive home and stay home for a couple of days)? Alternatively, couldn't you immunize everybody else within a short period of a week or so, and isolate the immunodeficient during that period?
Especially if any danger that vaccinating others might present to the immunodeficient is minimized in one of these ways, shouldn't we bear in mind that the immunodeficient would be those in the greatest danger if a smallpox epidemic ever got started?
The menace of the recently vaccinated to the vulnerable didn't exist when almost all the former were young children who stayed at home, or military personnel on bases. Permitting voluntary vaccinations by millions of Americans could kill thousands absent a really big-time public education plan. That is a necessary to the success of your proposals.
Check out the Smallpox Apocalpyse article on Strategy Page: http://www.strategypage.com/strategypolitics/default.asp