Is developing or producing the vaccine the costly bit? If producing, then what about creating more and patchworking them? It might reduce the monoculture type

Is developing or producing the vaccine the costly bit? If producing, then what about creating more and patchworking them? It might reduce the monoculture type issue. I.e. everyone gets the worst two, then two of the next 8/16, whatever models best. I assume this has already been modelled to death but asking in case anyone knows.