I agree on Skyway, great ride at night.
Also miss World of Motion, a very underrated ride.
And I would return Main Street to it's old charm with all the little shops.
If you never got to ride 20K, I wish it would run so more could have the experience. It shut down so long ago and was broke down often as well. It was a very different ride, not a big thrill by any means and the scenery was a little on the campy side, but a uniquely Disney ride.
As far as ones that could go:
In MK - Treehouse (or rehab it)
In Epcot - Body Wars (after the closing of JIYI)