Damn people are awesome. Someone built this already. 
And other results worth checking… https://www.google.com/search?q=js+diff+merge
One other approach, is to show a locked screen to begin with, and clicking an Edit button places a unique token on the data record that is associated to the user who clicked the button. So now that person is the only one with an unlocked screen so they can edit the fields.
When they are done and hit save, the token is removed from the data record and the next person can click edit (be sure to update the data state on the screen when edit is clicked – to pick up user 1’s changes).