I was thinking the Elk Late Trail. Not sure if that's the same thing as hiking up to 4 Corners, though it seems like there are very few alternatives when climbing Marcy from this side. Also, is it possible to take the Panther Gorge Route up and take the Van Hoevenberg trail back to get to your car, or are the trailheads to split up to make that useful? We're limited on time given that we only have a few days for our break. I've heard Elk Lake is a good 3-day hike if you end up doing the traverse of Haystack, Marcy, and Skylight. Is there a possibility of taking on a scramble up the Gorge just to tag Marcy?
Just curious: I've seen some of the photos of the slides on that side of the mountain. Are any of of them scramble-able/climbable?