MacBook Pro Kernel Panic on Boot - even without a hard drive installed My (Discrete, not Unibody) MBP (2007-ish) just started to kernel panic on boot.  

Pulled the HDD, which boots via USB on my Mini - hopefully ruling out a HDD or data/OS issue.

I've disconnected the Airport card as well as removed the memory SO-DIMMs and booted with one at a time.  Still kernel panics.

Tried the Apple Hardware Installer/Diagnostic DVD and it froze near the end (logic board testing...)

Wasn't able to get it to boot to try Tech Tool Pro diagnostics.

All signs are pointing to a logic board failure - am I missing anything?
I don't think you're missing anything. This all makes sense if you assume a dead logic board.
What makes you think that isn't the problem? Seems like plenty of evidence for it to me.