This is what I always think whenever the prospect of re-theming Pecos Bill's to fit with TBA: it seems like a solution in search of a problem, at least as far as thematic consistency goes. It's not like the current restaurant and Splash were themed to the same time or place. If anything, creating a little New Orleans area across from TBA that moves the Louisiana theming out from the fairly self-contained mountain and area behind the train tracks into Frontierland proper just makes Big Thunder's placement seem more awkward.
If what they want is somewhere to sell beignets and cajun food, that's a separate issue which might explain this. Thematically, though, it would be better if they could find a way to turn the area behind the train tracks into a Louisiana mini-land and put the restaurant there.