I really enjoyed reading your articles about the tranformation of consoles to portable ones!
One system I missed, altough very popular at that time, is the Magnavox Odyssey 2 aka Philips Videopac G7000 (hell, in France they called it Philips C52 and Radiola Jet 25).
That crazy 'little' system even had a full-size keyboard built-in and the games where very addictive..
I for once thought if there's a possibility that you (or any other person with the same amount of knowledge and imagination) can make a portable one of this baby?
Since this will be a big pain in the butt to do (because of the membrane keyboard and a complete different approach of a joystick) I certainly hope that you will find it a great challenge to accomplish.
If you want some more info, you can contact me.
In the past I've hacked that system myself, just for playing 4 different games from 1 EEPROM and a way to copy all games from the original cartridges without even opening them..
Perhaps that can be usefull for implementation..
Home of the Philips G7000 is a good site full of info about the console.
P.S. the system is still availabe at eBay