SA to MCO might be a niche. European leisure travel isn't high yield, but there's a lot of weathly south americans who like disney.
Still have a hard time imagining MCO as a hub because where are the connecting passengers coming from and where will they be going? Nashville to San Juan? ATL and CLT make such sense because ther are in the middle of the SE US not at one corner. MIA makes sense as a funnel to points south and because of the inherent size of south florida.