Whether it works out with Allen or not. He played this very well. Work him in with the 3s see how he does. Throw some number 2 reps in. See how he does. Give him second half of game 1. See how he does. Etc etc.
He had a plan and is Josh sunk...he would be all in on AJ or Nate. When he didn't. You give him the 3rd game. A dress rehearsal against real competition. If he fails. Nate is your starter. If he doesnt. You have your QB for the next 10 years.
Love him or hate him. He has a plan for everything and sticks to it.
Good luck Allen. You may need it