The key point of contention here is, can you make the Muppets fit a roller coaster? Yes you CAN. Is a roller coaster the best use of the IP, most likely no. Fans of the Muppets are not happy that the ride they will occupy is not the best medium to display the full gamut of their appeal. There is no room for Statler and Waldorf, no Sam the Eagle, no Fozzie jokes, etc....
If this was a coaster that stopped and had show scenes like The Mummy, then yeah it could be a much better fit, but thats not the type of coaster they have on their hands. Everything that has to do with the Muppets has to be done in the pre-show because once the coaster launches there isnt time for anything else other than cutouts.