And it was done with ex players and most of the prominent voices in football kicking and screaming. That’s my point really, football always remember to be resistant to change, and it has to be forced in rather than welcomed.
Relative to some North American sports, changes in the EPL were behind the times, but even so, in most NA sports, changes have also been slow and heavily resisted/criticized. Replay in the NFL was constantly criticized in the beginning and it was resisted. The extent of the replay available and what plays can be challenged is still debated heavily.
MLB, the NBA and the NHL have also been introducing more replay and this has been resisted and criticized as slowing down the games and being too interventionist. I'm pretty sure that even some of the umpire/referee unions have resisted the use of replays. There has been more debate recently, I think warranted, about the NBA and how much replays can potentially slow the game down, especially in the playoffs and in particular near the end of games
Ear piece should only be allowed when the ball is out of play, I see no problem with that. It will make the game much more dynamic allowing coaches to continuously out manoeuvre each other adding another level of excitement.
That would be better than constant communication. In the NFL, one coach can communicate to the quarterback through a one way microphone (same applies to one designated player on defense). Communication is allowed after plays and open until there is 15 seconds left on the 40 second play clock.
Most of the communication is play calling. Some QBs, like Manning or Brady, are/were known to be able to completely ignore these play calls. Others, particularly younger quarterbacks, are not only told plays but the coach can also relay messages about the plays the defense might run depending on the way they set up. Some teams run faster offenses and get to the line of scrimmage faster so the coaches can see the defense and communicate to the QB up to the point of snapping the ball, including adjustments that should be made or who might be blitzing. So you could see football managers utilizing it differently and a lot might depend on the relationship between the manager and the captain
I was watching rugby (I think) a few years ago and it was interesting that the ref was in constant communication with another official watching the game from a booth in the stadium. I think that system is pretty unique and it's interesting. That constant communication also probably betters the officiating on the field and speeds up the replay process.