Sounds like an interesting idea. While I have no idea if something like this will be made for CC4 or not, you can already today get access to all the data needed, so that should be able to be done with an add-on, meaning even if it isn't put into CC4 by default, it should be possible to write for anyone with a bit of programming experience and put in without PF having to add anything to pave the way.

This is more or less what I am doing in my dynamic dungeons project. Unfortunately, I haven't been able to pick it back up in a long time, but it still exists as a proof of concept for this functionality. Hopefully I can finish it one day. There is a video showing it in action linked from the beginning of the article:

If you name them sensibly, you can achieve the same (But you do need to use a command, not the GUI). Say you have a bunch of layers with different kinds of GM secrets, then you can simply name them GM Secret Doors, GM Secret Traps, GM Secret Secrets, etc. Now, you can toggle the visibility of all of them with TOGLF GM*, with the companion commands SHOWF and HIDEF. ('F' here means 'Filter').

Here's the map for anyone interested.

Looks like I'll be streaming again.

In this session, we have a peaceful forest where nothing at all happens. Completely safe, I swear. Just leave your weapons at the entrance.

As usual, the stream is available on YouTube. You should find the time in your timezone in the left forum sidebar, or by visiting the video page. See you all there.