This is the second post suggesting a button for this - the first you deleted yesterday after no response.
Regarding your suggestion - it is hardly a burden as it stands to click on an Icon to lock a Layer. How is saving a few seconds of such a benefit?
As Ashley always states regarding suggestions - a good case needs to be provided with good reasoning why a new function should be added, and of what benefit it would be to the majority of users.
Whilst your suggestion would be a nice benefit, does it justify the development time needed to implement?
Maybe it may be already on Ashley's to do list for C3, but I can't see it being of use for C2.