Its a problem right, if one user editing and he forget to unlock and went on break or vacation, At that time, it will be hard right, So if we show some error /warning like someone is editing, then it will be great right rather than locking.

What do you think will be the level of effort ?

I've see that touch UI solution and its great, but  all our authors is still using Classic UI and they need the solution in Classic UI ? Any suggestions are appreciated. 

I have a Use case where I need to let the Aem authors show a warning that If any other author is editing the same page in Classic UI at component level , Like if "John" is editing text component, We need to let other authors show the warning that if they are trying to edit the same component in the ...