I think you're making a big mistake in assuming that being a private pilot automatically means that you don't strive for the same level of competence and expertise as a commercial pilot does. Many don't, it's true, and there's not such a strict regime for recurrent training, but many private pilots have done things, and reached levels of competency that most commercial pilots could only dream of. I for one am not satisifed with anything other than professional performance from my flying, and am always trying to improve with new challenges, and refining old techniques.
A couple of years ago, with just 150 hours under my belt, I took a C172S from Florida to California and back, meandering across the country over 5 weeks with a tent, and no set route. It worked very well, and was a great 70 hours flying into a huge variety of different airports and environments. Ideal hour building, if hour building is what you're after (I did it for the sheer joy of it).
Do you just want the challenging and interesting flying, or also the ground-based challenges to go with it? (ie. Africa
) I'd class a flight to South Africa, or India, or something like that as an 'Expedition'. To many private pilots, a bimble to Monza is just a short weekend break
(But a great idea none-the-less, it looks like a lovely trip!)