FIFA has guidelines as to how long each stoppage in play should occur for. Added time is currently calculated like this. If it takes 30 seconds for a goal kick to be taken but the keeper takes a minute only 30 of those seconds are considered unnatural and are added onto stoppage time. So, they allow a certain amount of time for each stoppage to occur and then anything over that allocated time is adjudged to be excessive and SHOULD be added on. As discussed previously this is often not the case.
Because of how football is played the ball goes out constantly and in addition to this players also foul each other constantly. Foul counts in games can reach a total of 30 between the two teams very easily. That’s every field player committing one foul and half of them committing two. Stoppages are going to happen. But the amount of time that they happen for is reduceable.
I think a timer for stoppages would work well in football, it would increase the amount of times the ball is in play. The more times the ball is in play the more likely there is going to be a goal or some type of action. Football like any sport must constantly evolve its rules in order to keep up with safety, but also to keep the sport interesting and relevant.
Without this the game is in danger of becoming stale and boring. A stoppage shot clock is a more subtle way of increasing entertainment value. Entertainment value being more action for the time and in some cases money you spend to watch something.