Pin Layers to Top of Timeline

My idea would be to be able to *pin* selected layers to the top of the timeline, much like *pinned* comments or threads or posts get pinned to the top. These wouldn't necessarily be locked in the traditional sense of locking a layer in After Effects (although they could be), but would be "stuck" to the top of the timeline, with any new layers automatically inserted below them. As such, if you created a new Null Layer, it would be generated below the *pinned* layers, as opposed to at the top of the layer stack. This way layers that always need to be on top would remain there no matter what content is added or new layers are generated. Ideally this could be turned on and off at will, like Guide Layers, with the layer that is not *pinned* reverting to regular layer behavior in the layer stack. It could also be interesting if a "floating" window of these *pinned* layers existed that was always visible at top, although with the ability to turn this feature on or off so as to not clutter the timeline unecessarily. 

I think this would be useful for things like audio (which I almost always have either at the bottom or at the top) and especially for adjustment layers or layers acting as overlays that affect the entire composition and thus always need to be at the top of the layer stack.