I can see where you're coming from. I'd just suggest making a new account with no new strategies, unit bonuses, etc., and playing as countries you are inexperienced with or with strategies you rarely use. Or better yet, make a larger game with teams, ally with him, and show him by example how to get better.
I agree that a handicap could be useful in his situation, but it seems like a pretty rare circumstance. Still, I expect it would be easy to set up (something like reducing all units' HP by 1 or 2 would have a pretty even effect on all strategies and be easy to set up).