That is a nice way to disinguish pages that are finished and pages that need work. An, off course, to prevent pages from changing.

I understand there are some challenges, like multipage stories and master items, but maybe the lock function should take that into account, a dialog that gives the user the choice: 'The pages you are going to lock contain parts of stories that are connected to unlocked pages. Do you want InDesign to split those stories? Or do you want a 'soft lock' that locks all positions, but allows text to reflow?'

And then: a fully locked page will have a black padlock icon, and a smart / soft locked page may have a gray padlock. Or something.