I suspect the FDA will try to inhibit this as much as possible. Once the actual helpful intestinal flora are identified, they won’t bring in much $$$ to big pharma.
Things are entirely too complicated for an easy scheme. The amount of research currently ongoing in this is just staggering. Right now, the big bucks are in creating and patenting particular strains of bacteria, but this alone won’t do the trick, as a particular bacteria works in conjunction with a hundred other variables.