Everyone are throwing ideas to rework many aspects of dnd, most of them making the martial better and more interesting to play than just attacking and doing nothing else. So here's my idea: let's make extra attack be a free attack every turn that isn't part of your action. Of course, it makes action surge a lot weaker, but it opens tons of options for martials, allowing more strategies and, more importantly, more rp flavor expressed through the mechanics of the game.

Tired of running after a target? Now you can dash to reach them and still make an attack. Wanna play defensive? Dodge as an action and attack only once. Want to help your ally for rp or tactical reasons? You can do it and still attack once. Have a cool idea for a prepared action but "it's not worth to attack once as a prepared action when I can attack twice as an action instead"? Now you can prepare an action and still attack once.

Being a martial will still be simple and most people will keep attacking twice per turn and do nothing else, but when they must do something else, it doesn't just feel like a pure waste and allows interesting decision making for advanced tacticians or rp enthusiasts.

Of course, we would need to rethink the current system of cantrips scaling like the extra attacks (because a half caster could attack once AND do a cantrip balanced to be used as the only action of the turn). And I'm sure many of you would have interesting ideas about how to deal with that.