I have prototypes of an IO board that is in development for another
project, however there is a plan to make this available (probably via
Aleph) sometime early next year.

It has the following rough spec (Insert Usual Disclaimer here)

Cool runner CPLD- Bus handling etc.
FPGA (XC2-150) - Configure as you like, connects to 4 ports which
provide augmented high speed serial IO (SPI etc). There will also be a
number of small cards that connect into this port format to provide
sensing input etc (designed for mobile robots, remote sensing etc).
Atmel 128 connects to FPGA and CPLD.
Some RAM. Buffer for Data capture.
Data flash to hold FPGA config if needed, this allows the board to run
as an ATMEL 128 + FPGA board in its own right without a loon attached.

The board has been designed so that it can be mostly hand soldered and
thus built up as desired, although ready built versions will also be
available (TBD).

I will of course post more details if and when it becomes available.
The design will be "Open" but probably in a different way to the Balloon
board this is very much TBD.

The board does not provide 16 bit IO to a connector so may not suit your
need. (I'll be happy to quote.....)

David Bisset
iTechnic Ltd