@Megamig
I have several ideas myself of what to do with my X1000's Xena.
The only reason I'm
not using is because I don't have time - but I still find it interesting.
My ideas are these:
1) A Sinclair Microdrive controller. I know of no hardware Microdrive interfaces apart from those in Spectrums and QLs. Archival and restoration of microdrives could be so much easier with an AmigaOS-based interface. As the microdrive is really just a serially connected stereo tape player, and all the decoding is done in software, the XMOS would be perfect for this sort of thing - the bits coming back off the microdrive could be decoded by the XMOS on the fly, returning the data in a sensible format.
2) A floppy disk controller. The Catweasel has proven that there's a demand for using old floppies on new machines. The I/O ports on the Xorro should easily do for connecting a floppy drive, meaning all new Amiga machines can have floppy drives built-in, allowing you to install your Classic Amiga software via WHDLoad
3) A SID chip interface. There's nothing quite like the true analogue sound of a SID chip. Emulations are good, but never the same, any more than an MP3 is the same as a good LP. Digital sound will always be an approximation of true analogue sound.
Every now and again I come up with other daft ideas.

Of course, many of you will say these are silly ideas, but for ME they'd be fun to implement and would have some kind of use. Could they be done in other ways with other connections? Maybe - but having a fast controller like this does lend itself quite well to things like these.
The only reason I've not done so is simply because I don't have time, but that doesn't stop me appreciating the potential of what's there, and I still intend to play with it more, one day.