You’re talking theory versus what would happen in practice, and I think we all know that if vaccines were made mandatory that whoever had the most lobby money would be on or off the list of mandatory vaccines.
I’m afraid you are striving for perfection in an imperfect world. Knowing what we do about the dangers of these diseases and the almost complete safety of vaccines, the risk/benefit ratio is clearly in favor of vaccination.
As Thomas Sowell said, there are no solutions, only tradeoffs.