Go to the Arduino competitor forums, and there just isn't that much going on.
can you share what method or chips you were going to use to make the board 5V+ tolerant?
I also see the Arduino "backplane" as being a limitation on the system
This is a bugbear of mine.
Anything in particular?
As soon as the DUE is launched and people see tinkering going on with it, interest will come.
the bootloader for the arm
overkill for most things