That's basically what a customer care rep and their sup needs to do for you to get a one-year contract on a phone purchased with an Early Upgrade. You purchase the phone using the Early Upgrade. The rep then adds a manual equipment charge (read: debit) for the difference between one-year and two-year contract pricing to your line, and then gets a supervisor to manually change the contract date to reflect the one-year contract status. To make this easier on you and customer care, order the phone and then call customer care after you receive the phone and they can make those changes.
And, yes I've seen that done at my call center.