Game management is impossible if you don't know if the game is 90, 95, 100 or 105 minutes long. There should be 2 clocks in every stadium running concurrently. One for the 90 minutes normal time, the other for 'obvious' stoppage time (var, on field treatment, goal celebrations, substitutions) which is controlled by a 5th official.
At their own discretion, the referee can add extra minutes for what they deem time wasting on to the 'obvious' stoppages.
Transparency is absolutely essential for proper game management.
Anyways, that's my annual brainwave. Hope you like it.