Epcot - demolish the barges and replace with something more covert.lets hear it
MK - bulldoze the go-karts and replace with a massive people eater, I'd suggest an indoor soarin/FOP/etc experience to mix it up (I know people may not all like it, but they'll love it once they ride it). Something actually TOMORROWLAND-ish.
AK - revisit dinoland. I'm okay with the theme, keep it, but refresh it. Re-imagine the ride, even if it's indiana jones, etc. There's a 3D dino hunter game out there... this could be re-imagined as an interactive game where you are capturing dinosaurs.
HS - Retheme and rethink the Little Mermaid/Dance party/Launch Bay area. Something really cool could be there... not sure what... but it needs a reason for existing.