Figuring that it would be pretty easy to hack this with a soldering iron, I pulled up the schematics of the 'chumbilical' and went to work.  I don't have an O scope, so I metered a few things and made a best guess.  I almost have it working, but not quite;

All I did was take the P11 (P33V Backup) and short it to P9 (Chumby Reset).  From metering, it looks like P11 goes high whenever power is connected. 

Pulsing P9 works, but connecting P11 straight to it doesn't work.  I'm thinking that the debounce on P9 is keeping the chumby from powering on.  I could use a ucontroller to pulse P9, but this should be easy just with discretes. 

Thoughts?