We have little idea what Red will do, so most of this is guessing. Here is another guess:
Based on what Red has said, we will play multiple defenses to suit the talent on the roster. This does not rule out playing zone at times. The "3 guard offense" has never been mentioned specifically by Red (I think). I would tend to think he would like to play an aggressive, pressure man defense with players that are capable of defending multiple positions. This could get players like Judah and JJ and Chance on the floor at the same time, but not primarily with the intent of a 3 guard offense. The intent would be defensive pressure.
If that is the case, swing players like Chance, Bell, Q, and Taylor will see their time as "forwards" in a positionless offense, along with Benny and Mal.
I just don't see Q being the back up PG, unless that is the only option. His skill set is much better suited as a "3" or point forward type.
These might be some of the reasons why Red is targeting another guard. He will need a PG even if Judah comes back.