Good question. Perhaps something with ADB and ClockwordMod recovery?
I've not tried this myself, but perhaps something like this. Take the tcc8900_mtd.img file, unpack using tccunpack. This gives you boot.img and system.img (ditch the recovery.img). Assuming you already have clockwordmod on your pad, boot to recovery, and use adb to write over the boot and system partitions?
Sorry, I know it's pretty vague. Maybe I'll give it a try one of these days (hopefully I won't brick my pad!) and report on it.
Edit: I hope someone more knowledgeable chimes in!
No fastboot, AFAIK. Yeah, I guess update.zip package may be the way to go since ClockworkMod supports that. I've never built one before though - should be interesting
Start with a working zip file and carefully read the META-INF/com/google/android/update-script and/or updater-script (both exist in the coby update and have different syntax).