There are obviously numerous locally-optimal strategies for bacterial colonies in one's mouth (and gut, etc) as the population of bacteria varies widely across

There are obviously numerous locally-optimal strategies for bacterial colonies in one's mouth (and gut, etc) as the population of bacteria varies widely across individual people. That's not to suggest that knocking out one or two specific functions is going to accomplish recolonization, or that we should even trust the effort to be wise in the medium-/long-term in light of gene transfer or migration into the gut and elsewhere, but the broad idea of pursuing recolonization by less destructive bacteria isn't without merit in itself.