I actually had an idea about something similar. Not a real PSP, but a portable, battery operated device with built-in LCD. The basics would be to keep the compatibility with the original Minimig. To reach that goal, following things would be required for the design:
* 4-layer board (to bring the size down)
* Try to find a single memory chip solution
* Add a voltage converter and charger unit for LiPo-batteries
* Use a analog input TFT (RGB or S-video)
* Add a headphone amp with volume control
* Allow connection of external TV, joystick and power
* Built-in keypad that emulates one of the sticks (the mouse/keyboard will be a hard part to fix)
The ultimate would be to eliminate the MC68SEC000 entirely (replacing it with the open source softcore), but then we are talking about BGA packaged FPGAs (I think) and we have a unit that can't be hand built.
