> I want Gentoo that has been prepared as if the user just recompiled every goddamned program that makes up the core os, build desiderata and all waiting for me to make another change.

You likely don't want that. You can expect compiled objects to be in a 10:1 ratio compared to the final build size. Rust is closer to 30:1 in my experience so far. Then you have projects that vastly exceed that.

As a dev, I'm constantly struggling with disk space with just the projects I'm working on.

This doesn't even begin to handle the issue of contained/reproducible builds.

And with things such as LTO, you might be waiting at the "linking" step way longer than what you might think.

I don't think you realize how GOOD gentoo makes it already, considering all the variables in question. You can rebuild and patch the entire system, from start to finish, with a single command. Take a moment to appreciate this fact alone.