Looking for an express to dynamically adjust timing in my comp

What you want simply is not possible. Expressions have no way of modifying source, comp or project properties as would be required in your case. And quite generally I concur with Rick. If you expect AE to do this for you, then you are essentially using the program wrong. That does not preclude that it could not be faked to some extent using time-remapping and complex expressions, but it would be anything but intuitive because the actual initial timing and trimming would never visually change in the timeline and it would be more confusing than it's worth. Similarly, there could be some scripts that could help, but they would be equally unintuitive after a while. This is really stuff that should be done in Premiere by either having a rough cut as reference or finishing the project based on rendered clips that have enough extra head to allow for trims.

Mylenium

There is no Ripple Edit function in After Effects because After Effects is not a video editing app. Never was. Is not intended for editing.

I suggest that you render your nested comps and do the editing in Premiere Pro or any other NLE. FYI, more than 90% of my comps are under seven seconds and one shot. Some of my comps and animations are only along as a single phrase or maybe a sentence of narration, but I never edit in AE. On a very rare occasion, when timing, sound, and final tweaking is not necessary to create a suitable project I'll nest a half dozen comps in a final comp to create something that might run as long as 30 seconds, but that is a very rare workflow.