Adam, I read "during the shot" to be within the frame of continuous motion.
Assuming B2's foul was after continuous motion started, the ball remains live until A1 either completes the shot, ceases to shoot, or commits an infraction of the rules. Or, I guess it is technically possible for A to call a timeout before A1 releases the try....but I doubt that will ever be seen.
Since the ball remains live, A1 can, technically speaking, still commit a player control foul.
Should it be called? There might be that once in 20 years play where it would make sense....otherwise, probably not.
You really can't let get a shot off illegally, however. That really wouldn't be fair.
What can you do?
Maybe,
, B2's foul was just before A1 started the shooting motion, making the ball dead before A1 pushed off.
If the second foul is after the release, it is often easy to ignore the last contact as the first contact often contributes to the second contact.