This.
But of course a lot will probably have to do with the hopeful turnaround. If they want to get it done in 2 years, they will probably have to rush. There will obviously have to be a lengthy time SM will be closed. It's not the same kind of refurbishment as POTC with the red-headed lady. This is obviously a complete overhaul.
However, they can probably get away with not having to do massive overall structural work (just animated characters) if they keep the bayou theme intact for much of the ride. But I probably have NO idea what I am talking about and just throwing spitballs.
As for HM, it is ironic that this comes up here. The whole notion of haunted houses was something created in the early 1900's. Houses built in the 1600's, 1700's, and 1800's were still standing and were becoming increasingly dilapidated. Kids and teens would hang out there and vandalize them. So towns people would spook them to keep them out. That actually took place not far off from the time period that Tiana lived.
That said, though, it's too far from where Splash is to make a seamless turn of the century theme.