I've checked my documentation:
- Keep drivers during Sysprep: HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Setup\Sysprep\Settings\sppnp\PersistAllDeviceInstalls = 1
This should do the trick without fiddling too much with the unattend.xml.
You don't need Distribution Package per se. You could simply use the "execute file" action.