Explicit list of user-chosen packages

One thing that I love about Gentoo Linux right now is that I have a "world file", which lists every package I have explicitly chosen to have installed on my system. It's not a perfect solution, but I think it's nicer than Aptitude's approach of flagging packages as "automatically installed". It should work off of dependency graph analysis.

Removing packages that are dependants of other packages should remove the dependant package and all remaining unneeded and unwanted dependencies.

For example, if I have a clean installation, my package list is simply "ubuntu-desktop". If I wish to remove Mozilla Firefox, APT should figure out that it is installed through being a dependency of "ubuntu-desktop" and prompt me to remove that package, along with all of its dependencies. Importantly, though, it should give me the option to keep the remaining dependencies and add them to my explicit package list. This would require a careful refactoring of dependencies in order to keep this managable for the every-day user.

If, after removing Firefox and adding all other dependencies of ubuntu-desktop to my package list, I then decide to install ubuntu-desktop again, Firefox would be reinstalled, and the package list would have redundant items in. I think some sort of interface for maintaining a package list would be necessary - there may be cases whereby users wish to explicitly say that they want these packages to be installed even though they are currently installed as dependencies of other packages. This means that if a dependant package's dependencies change, it won't be automatically removed.

Sound like a plan?