Probably a bit late to squeeze this one into v8, but here’s an idea that would make working with assemblies much quicker imo.
On almost every audio mixer, and the Layer panel is analogous, on each channel/layer there’s what’s called a Solo button. It’s the same thing as One Layer On in the Layer panel, but not buried in a menu, and it doesn’t affect your mute/On settings although it temporarily disables them.
So when you toggle a layer on by pressing the solo button in the Layer panel, it acts exactly like One Layer On, but then when you toggle it off, there exists a One Layer Off that returns everything back to the way it was previously.