I've been able to put my hands on Daniele's laptop and these are the results. Adding "radeon" to /etc/conf.d/modules fixes the issue for him, and I'm sure it does for everybody.
Given this, I could be able to implement a workaround to the mess they (deliberately?) created. gpu-detector is already able to detect if fglrx.ko supports the current GPU(s) PCI IDs and decide whether to load it or not. It would be easy to add a simple "modprobe radeon modeset=1" if radeon DDX is selected. Then, the Installer should be able to detect that OSS drivers are in use and copy /etc/conf.d/modules over. This worked here. -- Fabio Erculiani
