Here's my stance I posted in another thread:
This would make the game more realistic. In the NFL teams aren't limited to what formations and routes they can run. I should be able to create any formation I want, with any route I want in every play. It's called football. But also in t the NFL, Teams spend a lot of time creating playbooks and adding plays to them after each week to prepare for their next opponent. This aspect should be in Madden as well. Everybody's offense and defense would be so much more deep. There would be a lot more variety.
Also, this would decrease hot routing. Again, look at the NFL. QB's don't change all their receiver's routes at the line every single play, but in Madden this is the norm. Most top players don't run a passing play without doing at least one hot route. Why? Because they don't have their own plays like the teams in real life do, so they have to create them at the line everytime, which is unrealistic.
This also applies to the defense. It's unrealistic to go around playmakering and moving all of your defenders before the snap. They should already be in position with the assignment you want them to have, just like in real life. And this would also help the defense out tremendously because you don't have to worry about pre-snap adjustments against quick snappers.