For working with solo layers, I often need a second level of soloing.
In compositions with over 100 layers, after soloing 20+ layers, I often want to solo a few of them without affecting the current solo list.
Pre-composing usually impacts absolute parameters, and I don't want to tweak them using JS control layers.
A double-solo or multi-level solo system, where the user can choose the number of solo levels, would be a handy feature to work with.