So, it seems that your argument is that a new thrilling headliner is what MK needs to address the long lines. But, won't that just attract more people to an already overcrowded park? And, a thrilling headliner won't address the long lines at the non-thrill rides which tend to have a lot of riders who won't meet the height requirements of a coaster.
I don't know... there have been a LOT of discussions about how to address the overcrowding of MK, including arguments like the above that new high-capacity attractions are needed to eat the crowds. I don't see a coaster/thrill ride as the answer, as it has a limited set of riders, and could possibly attract more thrill-seeking crowds with a limited set of rides that appeal to that demographic. That could just result in longer lines at the other thrill rides. As other have stated in the past, MK could benefit from a high-capacity attraction. But, IMHO, that should not be a thrill-ride/coaster. MK needs crowd-eating attractions that have no rider restrictions, to really be able to address the lines at all of the attractions in the park.
Plus, MK is not a thrill ride park. There are plenty of parks that are more thrill-ride oriented. I don't see that WDW needs to compete with those. That gets to the discussion of Theme Park vs Amusement Park.
Bringing this reply back on topic... A high-capacity replacement for the speedway might be a good solution.
amusement park vs. theme park discussion... it's the fact that the most popular park in the world doesn't even have a world class themed thrill ride.
Theme parks have the full spectrum except with theme -- there is no defending that. Also the fact how the most popular park in the world doesn't have a ride that so many park goers would love is ludacris.
I agree that the best thing would be a high capacity attraction (even something like Indy), but the height requirement logic is silly since less people can ride it yet they almost always have higher waits as they usually are the best themed. It's long overdue... as in decades.
But in the meantime, the most important thing is that the park gets a super-headliner. I'm talking about Indy, JTTCOTE, Splash, Shanghai/Paris/Disneyland Potc, Tower of Terror, Radiator Springs Racers, Spider-Man, Forbidden Journey. Fun fact... all of those but Pirates has a height requirement. The main thing that deters Is the fact that a coaster is a Coaster, so by having a thrill/dark ride hybrid like all of the ones mentioned many people that dislike coasters will still ride. It's the ones with little kids that won't.
What if we get Beauty & The Beast in Fantasyland (no height requirement) & a Wall-e 40" height requirement attraction. And in the meantime fix Space Mountain. That would work and neither would have to be epic scale attractions... just e-tickets.
Maybe a Coaster is not the best idea right now if they want to bring the Coaster people to Hollywood Studios, but the fact that MK hasn't gotten an E-ticket in over 20 years is a disgrace. So perhaps a high capacity E-ticket dark ride would work. And people will say "oh more people will go" but it HAS to happen. There has to be another E-ticket to at least improve MK's outdated lineup, and while it is strong compared to the other WDW parks, IOA has less than half the attendance with far lower waits, but has great rides.
They need to add a new E-ticket (maybe not a headliner, but at least an E-ticket) and don't really market it much and instead more word of mouth, or open it alongside a new EPCOT attraction.
Just to use common sense.