I don't ask for food upgrades, however there is a Chinese on the just eat near here where you have to put "make sure you send CHIPS, not RICE! " if you get the kids chicken balls + chips... Because if you don't, they send rice EVERY TIME.
I might try your trick though Michael. I'll order a small chips and then in the box I'm going to put "can I also have a large stuffed crust Pepperoni pizza, some chicken pakora and three cans of coke". You never know.