A short yardage QB? Given the timing and rhythm nature of the league I don’t see QB by committee happening, too many people need to think “3 1 thousand” is the same time and same distance for you to be swapping QBs in and out. And in general with less room to work tight in the end zone is considered to be the spot QBs need to be more accurate, not less, so you’re really not going to have a guy who’s not good enough for midfield but good enough to close the drive.
With the way a qb may hit a dozen receivers in a game..with half or more of them only catching 1 or 2 passes for entire game...”timing and rhythym” become overrated...especially given that many if not most teams run the ball 55 to 60% inside the opposition’s 30...see post #19 for details
Most passes inside the 30 of the opposition these days isn't a direct end zone route...more & more relying upon YAC. The toughest defensive assignments are when they know the QB has legs for either scrambling for positive yardage or scrambling for extra finding a receiver open.
This isn't simplistic "good enough" or "not good enough" ... or they wouldn't likely be in an NFL uniform... it's about throwing wrinkles to the defense
In baseball, managers will bring in lefties to throw to lefty batters. They might bring in a speedy pinchrunner @ 3b to force the infield to play in with less than 2 outs...
Your "not good enough for midfield" comment is like critiquing a baseball manager who brings in a reliever for a starter ... even tho that reliever is "not good enough" for for the starting rotation.