If it was another packaging system you were looking for, as opposed to specifically wanting to install Gentoo, why not have a look at Slackware?

Slackware specific packages install with pkgtool, every thing else is compled from source, (usually, > ./configure >make >make intall).

Some find it difficult to begin with, but if I can manage to get it up and running, I'm sure that the vast majority of those subscribing to this list, can have a working installation in a shorter time than it takes me! -- John Seago