I have always found this idea interesting, for the same reasons you do. However, it is not a
new idea. Dr. Harry Smith was one of the first if not the first to test the concept. He was
trying to treat scours (E. coli) in beef and dairy calves. I believe these results were
published in J. Bacteriology (ASM) in the 1970's.
Lactococcal phages, and recombinant phage lysis genes have been used in the dairy industry in
cheese fermentations to contrtol flavor.
An important aside to this idea is that several bacterial virulence determinants are carried by
phages, especially toxins. Therefore, like all good ideas, there is a downside.