That's what I was thinking. Turn the majority of the current Frontierland into a New Orleans Square, and utilize the expansion plot to make something similar to Western River Expedition (Make the IP Brother Bear or something).
A man can dream.
tl;dr -- Disney's not likely to add more 'frontier' themed attractions... ever.
Sorry to be bearer of bad news, but, without getting too much into politics, the whole 'frontier' paradigm is going to be more and more... problematic.
The sanitized notion of 'the frontier' which is of one of conquering wild nature -- while ignoring what happened to the Indians, or, making the Indians the bad guys -- isn't going to fly anymore.
The popular genre of The Western which had its heyday from pulp novels to silent films to talkies to television lasted almost a century, but has fallen out of favor with the exception of modern films dealing with very adult themes that would be out of place for Disney parks. The old Wild West stories of Hollywood no longer take place in the Wild West, they take place in such places like a galaxy far, far away (The Mandalorian).
Attempts to make G-Rated frontier movies popular fizzle (Disney's
Lone Ranger and
Call of the Wild). How many avid Daniel Boone or Davy Crockett fans are left? There are no Disney IPs based in 'the frontier' that are both popular and family-friendly (and avoid problematic stereotypes). And if they create their own brand new story and leave out the warts of history... Disney will be pilloried.
Disney itself has de-Wild-Westernized and de-Frontierized the land over the decades.
BTMR works in that it's set in "The West" at a certain time and deals solely with the events at one particular mine without getting into Manifest Destiny, Expansionism, or Colonialism. In the "more Disney" era, there isn't going to be another attraction like that without an IP attached to justify a budget... and there are no popular IPs available which aren't problematic. Perhaps something purely geographical like a Yellowstone attraction might work... but, where's the IP for it?
I've suggested that the whole area from HM to Liberty Square to BTMR to PotC be renamed to "The American Experience." A more encompassing theme makes disparate element 'fit' better, IMO.