I am a huge PP fan. But I have to say -- I think the C's have 3 guys who are effective back-up PGs. Of the 3 I favor Pritchard as the starter. He dives right in offensively -- good/reliable handle, he moves the ball, his 3 is ready, and defensively he is active. Smart is obviously the better defensive player, but to start a game, I vote for Payton. Schroder has had big games offensively and is a contributor, but he's inconsistent and I like him off the bench. Best of all worlds (IMO) the C's get there hands on a true starting PG (preferably with some size) and Pritchard gets 20-25 mpg as back-up PG and occasional 2.
If the best case scenario is Pritchard at the backup PG with 20-25 mpg, that's what the Celtics should do without the extra details you started with.
I agree that Brad needs to deal with the Smart/Schroder issue. But at the very least they should try to develop a well-rounded roster ASAP.