Then if he wants to eliminate that, sign the deal that's being offered. One year difference isn't much, and it certainly isn't for the dollars being discussed. Besides, if he outplays his deal, do you really think that the team wouldn't negotiate to extend him on the back end of it? And do so prior to the contract expiring?
Like I said, if his true concern is being able to hit the market early, the easiest solution is to play under the tag. Except, what Prescott wants is to have his cake and eat it too - he wants top of the market money for a QB, and short term deal to boot. The Cowboys completely screwed this negotiation up by being public with it, and also by putting the exclusive tag on him. The transition tag isn't a good move, because yes, you let other teams determine his value, but, if the Cowboys decide that Prescott isn't worth what he's being offered, they let him go for zero compensation. The proper move would have been the non-exclusive franchise tag, due to it being less money against the cap for one year, and it affords them compensation if he gets a deal elsewhere that the Cowboys aren't willing to give him.