I don't like the idea of lying, but flying J on an airline in which you have no points would seem like one way to make sure you are not in Y. I suppose you could be a little sneaky and fly J on an airline which is in an alliance with your base airline and then input your ff# much later after booking. Also, I would hope that your boss knows that (on most carriers), only full fare Y or something close to it is upgradeable.

Another potential excuse: "there was no inventory available in the upgraded class"... this is very often true on DL and several other carriers.