DHS should be the "thrill" park IMO. They've got the best start with RNRC, TOT and ST. It could be great for families as well with a Pixar Place expansion. Still, I would hope the MI coaster would be more of an adult coaster (given what a great coaster it could be) and that they could create an amazing Spider-man-type 4d ride around Incredibles.
In a perfect world, DHS would be expanded with:
• SW, with thrill rides
• Pixar, with MI and Incredibles for teens and adults; Bug's Life and Cars for kids
• a comprehensive ToonTown with tons of things for kids
WDW desperately needs something for the 11-24 age group (especially now that there's Potter). Each park can appeal to everyone, but each one should have it's niche as well. IMO, IOA is one of the best thrill parks in the country. DHS is the best suited of all of the WDW parks to expand their "thrill" offerings and take on IOA head-to-head.