Hi Daniel,
I'd be very interested to hear more about this project. I have two PD6s, one of which is still my primary recorder, the other has a busted DVDRAM drive so only gets used when I need more than 6 preamps. I love the direct outs, switchable power on the AUX I/O, the limiters, hardware switches instead of software etc. The main downside to using this machine is the constant changing and formatting of the discs, so if there's any way to use CF or SD I'd be a very happy man.
Other things to consider:
1. More accurate battery level indicator
2. Firewire recording while recording to disc
3. Bluetooth compatibility for a keyboard (hardware mod via usb port?)
Would love to hear more and help with testing, like I said I've got a spare PD6 gathering dust so can get to work straight away!
Keep in touch and well done!
Sam