Removing Splash Mountain would be the mistake, it's incredibly popular and one of the best Disney rides period. I'm sure there would be a huge backlash to get rid of it (and the left out all non-PC aspects from Song of the South, so there's really no fuel to use about it being racist). It even looks very good visually compared to the rest of the land. The imagineers themed the outside well, not overtly cartoonish enough to clash with the rest of Frontierland's more realistic style. The people who think it's bad or a poor fit for the land seem to be the vast minority.
As for it being southern themed and not "fitting" with Frontierland, Frontierland has always had influences of the "south". It's not "OldWestLand", there's a lot more to it than just that. Tom Sawyer takes place in Missouri along the Mississippi River. Davy Crockett, aka "King of the Wild Frontier", was from Tennessee. With his career primarily being based there as well as other southern states such as Texas. The land is not and has never been exclusive to the west.
I'm very glad the current idea is to keep the Riverboat and TSI. I admit that they're not attractions I generally do myself, but even for a casual observer they add SO much to the area visually. Things wouldn't look remotely as good without them. I would be very disappointed to lose them. There's plenty of room to expand this land without losing them, whoever said they should remove these attractions needs to be fired...
At this point, closing anything down would be two steps forward, one step back for MK. They're better off expanding as much as they can until they've completely run out of expansion space.
I agree that once people walk into Tomorrowland, they look at it and want to ride it. But it's definitely not an attraction thats popular enough that makes people WANT to go to Tomorrowland. Space Mountain makes people want to go to TL. Splash and Thunder make people want to go to Frontierland. Jungle Cruise and Pirates make people want to go to Adventureland. Haunted Mansion makes people want to go to Liberty Square. Peter Pan and 7 Dwarves coaster makes people want to go to Fantasyland.
Again, I'm usually always judging on non-regular theme park attenders. I was trying to get a point across that Tomorrowland has only ONE attraction that is really drawing people to the area simply but looking at the maps, knowing it's a coaster or an "E-Ticket"... Ect.
Buzz is definitely a draw to Tomorrowland. 50-70 min waits, usually. Especially during a thunderstorm.
Well then, a huge step for Tomorrowland would be to give the PeopleMover actual substance. So much of the TTA is empty tunnels with zero narration. Adding show scenes inside the tunnels would bring Tomorrowland to life and make the PeopleMover a must-see C-ticket.
Tomorrowland has a lot of wasted potential:
Stitch's Great Escape always half-full
Carousel of Progress always half-full
The PeopleMover not having a lot of substance inside the tunnels (if space is an issue, screen-based show scenes would be perfect)
Nothing on top of CoP (a B/C)
Nothing between Space/CoP (a C/D)
the Main Street parking lot (new attraction behind Buzz)
The Speedway (either make it futuristic, or demo it for Fantasyland)
The space behind the Speedway/Space Mt. (could fit 3-4 attractions)
Tomorrowland Terrace not being open regularly
Expanding/revamping Tomorrowland could help out considerably with MK capacity. There's room for 6-7 new attractions for Tomorrowland and 2-3 new attractions for Fantasyland if they properly used the space.