A person goes thru security,then heads over to the gift shop and buys a minature tube of toothpaste and a small bottle of mouthwash, then runs into the restroom and shoves the stuff down their underpants or socks, then heads over to their departure gate and boards their flight... Now what...
You know, I've thought of doing EXACTLT what you propose, just to outsmart the TSA goons (except I'd pick toothpaste and deodorant as the two 'essentials'). But I also assumed that the TSA must be at least smart enough as to have already ordered all airport merchants beyond the sterile area to remove all such items from their inventories.
But then, assuming the TSA has any brains is probably a poor assumption...