If you're an ex-Slackware user, I don't see why not. Might be fun, actually.
Then after a while of managing dependencies yourself, you'll get bored and whip up something that manages dependencies, which will get slower and slower due to NP-Complete and eventually you'll realize that you have reinvented Portage.
I honestly don't get why people still hug a language that does its best to emulate Java when they could just use Java and get a solid performance boost.
In which way?
Then don't emerge app-portage/gentoolkit, it doesn't even come with the base system.
Portage is bigger than everything else because it needs to be 10x as powerful as everything else to work with source code.