Although I can understand the desire for such a feature, I’m afraid that I’m against it. This is exactly the sort of thing that would weigh down with support with angry, “I CAN’T EDIT MY WORK AND I’M ON A DEADLINE I HATE YOU!” emails. 
Users manage to accidentally turn on script mode and revision mode all of the time, so I have no doubt that we’ll get plenty of users who would accidentally lock their documents and panic.
All the best,
Keith