One thought is if the Knicks do indeed start Quickley, it means our PG situation will be BETTER than last years - it means we have a better option than Payton/DSJ/Frank. Think of Quickley as fixing 2 things with 1 player:
Quickley fixes the starting lineup: he makes RJ and Randle better because he gives them a passing target and helps space the floor. His shooting is a skill that was completely lacking from the PG position last season - craziness!
Payton's a pretty competent all-around player - though his shooting is a glaring weakness. When he's on, he can stuff a statline - he has 17 career triple doubles. While he's above average in a number of areas, he isn't exceptional in any one, not enough to offset his shooting.
Payton on the bench becomes a better player - You get more value out of Payton if he's surrounded by athletic shooters - in this case, the Knicks bench is a much better unit that plays better to his skill set. Multiple shooters can hide his deficiency as can the running game. Obi/Knox/Bullock/Rivers give him a bunch of targets on the wing or on the break; and he has a few options for pick and roll partners (including Noel/Robinson).