tried a mix yesterday: 4 tbsp corn starch with ~1/8 tsp salt and one Emergen-C Energy+ packet (I had it laying around) with 20 oz water.
"chalky" doesn't start to describe it, though it did go down smoothy and my stomach didn't get upset and I wasn't gassy.
The recipe in the OP calls for more than twice as much cornstarch. That must come out like paste. Blech.
Dunno if I'd use it exclusively, but it worked okay. shrug.