Splitting a DMX universe over multiple arduino's shouldn't be much of a problem. Max's code is using a addressing() function to specify what channels to listen for based on button presses. You can very easily replace that with a DIPswitch or even hardcode it since you're not likely to change it once installed.
Please let us know your progress. I'm pretty much looking into the same thing. Be it at a much smaller scale with only 2 lines of 22 MegaBrites.