I don't necessarily think they needed to keep the Liberty Belle as an attraction
Overall, I like your alternative ideas, but I would just counter on this point: I think Magic Kingdom (and every park) needs more quality attractions that don't require waiting in long lines to experience. The Liberty Belle would always be a reliable option for something to do even if the park was slammed with crowds.
If the argument is that the island/the river provided the park aesthetic value, I’d say that the same level of aesthetic (trees, water, and a few place-making structures visible from the other side of the river) could very feasibly be achieved as part of the new expansion.
Could, yes. I am very skeptical and hope to be pleasantly surprised. Blog Mickey has a new article that seems to imply that the recent "Fun Map" artwork could very likely kind of be smoke and mirrors, over-exaggerating water and tree elements in order to (try to) placate concerns about the new aesthetics that are coming.
I hope it ends up looking incredible. And, frankly, it
has to, or Disney will never hear the end of it.
In fact, the list of additions to Disney World dating back to New Fantasyland suggest that, at the very least, this project will look good.
The TRON and Cosmic Rewind showbuildngs are not encouraging. But yes, good work has been done, and if we were to learn that the people who handled Fantasy Springs, say, were designing this, I'd feel a lot better about it.
I think we can all agree the integrity of the Haunted Mansion attraction experience is more valuable than that of Tom Sawyer Island.
It remains to be seen how the integrity of the Haunted Mansion queue is going to be preserved in the current plan, too. The Mansion no longer being along the banks of a river pretty fundamentally changes its stature and placement.
At that point, I’d rather they build the best version of what they’re setting out to build from the ground up vs. working around constraints to a compromise that really makes nobody happy.
I think the "pure expansion" option (like what Disney hinted at when they started talking about "Beyond Big Thunder") is the one that would make everyone happy (unless there are people out there who
actively wanted the Rivers of America and the Liberty Belle to no longer exist, but that would surely be a very tiny minority).