CrossRoads:
For example, use a wallwart 5V power supply, delete the 7805 regulator, add IO connectors that are more secure than plug-in headers, etc.
I would be careful with that advice. Modern switching wall warts should be fine, but if he gets a cheap, old linear based one, it could easily give 8V no load and fry his chips (yes, I made that mistake in my pic days).