Thank you also for the discussion.
Controlling a cell population in the body is yet another great challenge!
Maybe it could be more feasible if there were two sub-systems:
1. A new virus detector, it doesn't have to be based on B cells, an implantable device could perhaps fill that role at least as a first step.
2. A platform can produce a personalized vaccine. I made a toy version of this a few years ago for peptide vaccines [0].
2.1. On the software side there are minor challenges.
2.2. On the legal aspect of a personalized vaccine, its transport and administration, it is much more complicated, those are real challenges.