Actually we have something along those lines: using our command line utility you can install "packages" which should be a collection of classes for added functionality. Currently we have some well known libraries already available through the CLI by using "php oil install package htmlpurifier" for example, they're taken from Github and installed in the fuel/packages/<packagename> dir. Of course if you don't want CLI you can just download them and copy them to the right directory yourself.

We intend to create a repository for packages and classes installable through Oil directly into your Fuel install. At this time we are still using a single Github profile to fork any repo into that will be available through Oil package install: https://github.com/fuel-packages (install the packages without the "fuel-" prefix as their name)