Well interestingly enough (or not, depending) as a former Double Bass player I used to soak the callouses on my hands (essential for playing) in vinegar to keep them hard. I suppose a similar toughening action might occur on the balls, by causing the dead skin cells on the uppermost layer of the skin to harden, but you'd probably have to stop actually washing your balls too which I imagine would not be all that desirable.
Nor would having a scrotum with the feel of a tennis ball either, which would be the theoretical result of all this pickling. LOL