Re unlimited subs - there are a few interpretations of this. If it remains, once subbed off can't be subbed on again, then it's essentially just an increase to however many subs are on the bench... 6 outfield subs for PL... Which isn't a huge change.
However this changes by each tournament rule, so I assume it could mean rolling subs, players being subbed off and on again multiple times in a match. This would be an ENORMOUS change and would lead to specialists - a player being subbed on just to take free kicks, or a goalkeeper to save a penalty, or Fellaini being subbed on just to attack a corner. This would be awful IMO and would be damaging to the game.