You take a simple part of the game - shooting from a relatively close distance and let's see which team can handle the pressure with the entire game riding on a simple act.
Players miss PKs routinely under pressure. The making of a PK is not a given.
I think it would be fun if NBA teams were tied after OT to go to a FT contest. Everyone says Kobe or MJ or Seth Curry is clutch - let's see who really is with one shot. And you've got other teammates who would just melt under the pressure.