Is the source for FIRST's default implementation of the Cypress PSoC board available anywhere? Is it against the rules to modify the default firmware on that board?
There is no reason you can't set up a simple system that uses an I2C controller and HID comms on the PSoC board. If we are not able to get our hands on the default firmware, you can check out this article for a start:
http://www.cypress.com/?rID=39404