Sure, thought of it years ago and even approached my LHBS guy to see if he was interested. The problems that he mentioned were that the chemicals would have to be food grade. No problem with that but then he raised the issue that the packaging would have to be done on equipment certified for food handling in a facility certified for food handling, that inspectors would have to inspect the facility etc. That was enough to scare me off.
Beyond which I realized that chasing profiles was not the way to make the best beer, that most profiles were bogus etc. But 5.2 still sells like hotcakes so I suppose AJ's water salts might have sold.
A big problem in addition to finding realizable profiles (many of the popular ones aren't) is that most water contains calcium bicarbonate and I can't buy calcium bicarbonate. The only way to properly simulate such water is to add calcium carbonate and bubble CO2 through it. Few would be customers would be willing to do that (and I don't blame them as it's a waste of time in general). If you take out the calcium carbonate you can't get a good match because you aren't doing what nature did. Bottom line - it's not practical.