This has been suggested before but it is an interesting topic but I think 4 events should be considered especially given we added Skateboarding and Climbing with great success.
Winter Olympics:
Cross Country Running-super exciting, spectator and TV friendly. Adds a Team competition to the individual medals. Allows many more countries to participate and compete (no more add on Kenyan to Cross Country Skiing after a 2 month crash course...)
Cyclocross-if summer can have BMX why not a 1 hour super exciting race that could be held on the above Cross Country Course during the winter edition.
Summer Olympics:
Start with removing some events-shutter the Race Walk and 10,000 meter track race. Personally I think there is no need for a track race longer than the 3000 meter Steeple Chase...5KM and longer should be run on the road
Add Road 5KM and 10 KM (they could be run on part of the Marathon Course)
Add a 50 KM 5 person Ekideninstead of the Race Walk This would add more team competition to track and field. It could be fielded from the distance runners from other events. This could be a highlight for the middle weekend or the Opening Day.
Let me know what you think!