FYI - Same name as OP but not same person ... lol
This is similar to what ,I believe, the XYZerocart does (http://www.wctek.com/shop/home/28-xyzerocart.html
). An on-the-fly flashing of an eprom to spoof an actual cartridge.
I would love to know how to do this just for the sake of tinkering, but ultimately would probably spend the $$ on the already done work (Zerocart).
In the meantime I've taken an empty cartridge and mounted my Uno in it with a cut out for the USB port (allows me to apply power without disassembly) and hard wired it to the filament chip (to the actual chip so I do not block the contacts).
If nothing else I can simply pull the cartridge out of the printer, plug in power to the Uno and wait a few seconds, place the cartridge back and I'm up and running with a fresh 240m being reported.
Not sure about the serial number stuff or anything, I have just blocked the xyz.exe in my firewall and have had no issues.
I have the 1.0A running System Version 1.0.3. Only had it for a few weeks, but so far have clocked in 83 Lifetime hours.. Not brave enough to go custom FW just yet, atleast not until I get past the beginner stages of playing.