Can you post a youtube video of executing this? I'd say it can be made 1 in 500. If that many.
You have to weigh percentages in all pool games, and this ability is particularly important in one pocket. so, if the situation is as bleak as you make it out, and you really can't win the game, you should try to give yourself the best chance of winning, no matter how small. There may be other shots available, but I'm only discussing the most common "real world" reply - following the 1 in. With this in mind:
Scenario A: (posted shot)
1) if you make 1 and miss the 2 ball (or hit the 2 but don't make it), you just made your opponent's game ball. I would guess this would happen about 90% of the time. This is so because the 2 MUST be far out from the side pocket for it to be a makable shot with ball in hand (as your scenario states). That is, it's not "hanging" in the side in your scenario.
2) If you can hit the 2 and make it, you have a slim chance of scratching. Using the 90 degree rule, the cue ball would hit near the first diamond. I would guesstimate this happens 9.95% of the time.
3) You lose 99.95% of the time - by shooting your opponent's game ball.
Scenario B:
Now suppose you follow the 1 in and leave the "hanger" 2 with ball in hand. Well this shot is between a 50% and 99% shot depending on the level of player. Lower percentage for lefties, since they have to bridge funny. And I'm sure we've all seen this shot dogged for the cash. I've seen pros miss it.
Anyway, let's just say your opponent can make it 95% of the time. You either have a 5% chance of winning (which is pretty small) or a .05% chance of winning by shooting the posted shot.
Thus, playing the percentages and following the 1 in gives you 100 times greater chance of winning than trying the whack-attack hit-n-hope shot.
I recognize that the odds aren't in your favor either way, but I'd want all the advantage I can get. And I'd rather my opponent dog the shot than make the game ball for him.
-td