Frankly, I can't think of too many differences in en-route contingency planning in a large jet than in a smaller turbo-prop or going back even further, a DC3
Overall, my thoughts are that the number of possible problems would be less, e.g. Iceing at high levels is a low probability, but when I think of carrying icebergs on F27s, Viscounts etc. at lower levels, I'm glad I'm not there any more.
Capt. Claret is correct in saying en-route MEA poses no real problem in Australia for jets with 1 engine Inop, but on the 2 engined B777 an Afghanistan crossing with MEA up to 19,000 ft is not a problem there either.
About the only significant problem is that jets USUALLY are larger and heavier than their propeller driven counterparts, and the list of suitable airports for diversion reduces in accordance with aircraft size.
Regards,
Old Smokey