Not necessarily 5 on the line, goalkeeper the wall, still leaves 5 players placed strategically to grab the second ball. The only problem would be dealing with the offsides and handbags on the goal line.
I don't know if anyone has even thought about it to actually see if it works or not. If I was part of a football team I would try it in practice to see if it gives an advantage or takes it away. That I really don't know.
Clearly from 30 yards it would be a problem but from 20-22 yards, the ones we tend to give away it might work. It would have to be tested though. It might just put the opposition off a long shot and they take it short instead, but you work out a system to deal with that too.
Thinking out of the box; You could put 4 or 5 players on the goal line and bring the goalkeeper out to stand in the normal wall position 10 yards from the kicker. The goalkeeper would make a better wall by himself because he can use his hands. If they manage to get a shot past him you would...