Way cool Eberhard.
I've been jammed up with work and other projects and so haven't had a lot of time to spend on xmegaduino. That said, I hope to soon post a significant revision that makes it easier for arduino to support different boards and cpu families without needing to completely replace the bootloader or core. I hope upload changes soon, but this will be early work that shows direction but that doesn't work. Hopefully have it working in a couple more weeks.