Are you looking for something in the Zion area? What geographic area are you most interested in?

If you are looking at a wide area, I would highly recommend Yosemite. Many different routes that would fit your criteria, amazing scenery, lots of remote locations while still being supported by NPS infrastructure, and many many trailheads and bailout points to look into. Especially if you focus on the stuff east of Yosemite Valley (Vogelsaang, Merced, Tuoulumne Meadows, etc.)