I don't see why concussions need to be treated differently than any other kind of injury. Obviously concussions can lead to long-term issues in a way that muscle injuries can't, but in the short-term, they are just another type of injury that means the player can't continue.

The problem is with the teams. Either their medical staff aren't properly assessing the players, or they aren't taking concussions and head injuries seriously enough and want to let players stay on to save themselves from making a substitution they haven't planned.

Clubs shouldn't be pandered to, the rules shouldn't need to be changed for them to take concussion seriously. It doesn't matter if a player gets concussed in the 15th minute or the 85th, they shouldn't be allowed to come back onto the pitch and teams shouldn't get special substitutions for specific types of injury.