I have thought about a Jim Henson theme park since at least 1994. Since this would have been years before The Jim Henson Company sold off some of it's own properties, it would have been possible to have a replica of the Sesame Street set, a tour of Fraggle Rock, a Labrynth maze (possibly a ride), an oportunity to put shard into a Dark Crystal, and go into the homes of Kermit, Miss Piggy, Fozzie bear, and Gonzo (similar to how people at the Walt Disney World theme parks can go into the homes of Mickey, Donald, and other characters). There could also be gift shops selling merchandise relating to obscure characters and productions (wouldn't it be cool to have a set of Sam and Friends finger puppets? Or a big, stuffed Sweetums or Doglion doll? Or a Frog Prince PVC set?). The gift shops and waiting areas could also have televisions, showing many Henson productions, including really old, super obscure stuff.
And of course, there would be walk-arounds of the various muppets.
I had this idea before I knew about Sesame Place, and I guess with Disney currently owning the muppets, we can have walk-arounds and new attractions sometime in the future.
I posted a thread like this at The Muppet Newsflash Forum two months ago. You can go there and check my thread out.