Damn, they're making it hard for people to port stuff to it then. We're not gonna fix this on our side. However, we use very few globals. From the back of my head, only $roster and $installer. If you just export those to the global scope after they are created (in settings.php and admin/addon_install.php), everything should work fine.
If I were you, I'd complain to the joomla folks about the design decision though.