Inheritance, Module and/or Mixin Pattern for Oxide Plugins?

Is there any inheritance/module/mixin patterns in Oxide plugin development to extend/override methods in a referenced plugin, or is the best bet to just fork (copy, paste and rename) the plugin source code and make customizations that way?

The Zones Manager plugin seems like a great starting point for a Factions/Cities plugin I'm working on now, and I would like to extend and override some of the private methods defined there.