A few ways to improve association football

Association football (soccer) is by far my favorite sport.  While the rules of the beautiful game have remained (mostly) unchanged since its invention, there are a few rule changes that, if made, in my view, would make the game faster paced, higher scoring, and generally more entertaining. 

Replace throw-ins with kick-ins.  Players are not physically able to throw the ball with anywhere near the velocity that they can kick the ball.  If throw-ins were replaced by kick-ins, there would be many more goal-scoring opportunities in each match.

Allow hockey-like substitutions.  In hockey, there is no limit to the number of substitutions a team can make, and teams do not need to wait for a stoppage in play in order to make substitutions.  Whenever a player is tired, he can just skate to his team's bench and a teammate can sub on in his place.  As a result, when players are on the ice, they can give 100% of their effort without worrying about conserving energy (unless they are killing a power play, in which case the players on defense may not have an opportunity to skate to the bench).  By contrast, in football, only 3 substitutions are allowed per team per match.  As a result, players must conserve their energy.  If football allowed hockey-like, the game would be more action-packed and fast-paced.

For shoot-outs, have kickers kick from anywhere outside of the 18 yard box (or possibly further).  A shoot-out often referred to as "the lottery."  The reason is that, with kicks taken from 12 yards out, goalkeepers must guess which direction the shooter is going to kick in order to have any chance of saving the ball.  As a result, winning a shoot-out largely depends on luck.  If players were to shoot from outside the 18 yard box, goalkeepers would have  some chance of saving the kick without guessing.  As a result, winning a shootout would depend more on skill than on luck.

Make the goals slightly bigger.  Compared to other team sports, football is a rather low-scoring game.  Typically, matches end with 3 goals or fewer.  And, it is not at all rare for a match to end in a 0-0 tie.  I think it would make sense to experiment with making goals bigger so that the number of goals scored per match roughly doubled relative to its current level.  This increase would create more lead-changes without reducing the importance of a goal.

Suspend players that dive.  If an attacking player is fouled in an opponent's 18 yard box, his team is awarded a penalty kick.  Because it is much easier to score a penalty kick than it is to score from open play, attacking players often go to the ground without being contacted by a defender (i.e., dive), in order to give the impression that they have been fouled.  One way to reduce diving would be to have a committee of referees review videos of matches after they have completed.  If a player is deemed to have dived in this review, they could be suspended for a certain number of games.