When you're talking about leopard Sharks, Smoothhounds, Epaulettes, Bamboo Sharks, Catsharks, Nurse sharks & various species of rays - you need to realize that most of these species require different water temperature (some are cool water, & some others are warm water species).
Given the footprint of 8-10' in diameter that you've been stating so far - I would suggest sticking with the small bottom-dwelling sharks - like Coral Catsharks, Bamboos, or Epaulettes. And the Round rays for your rays.
Also with any species you need to consider the nature of the species in question, such as is it a Bottom-dwelling or an active Swimming species. Is it a Non-ORV or ORV (Obligated Ram Ventilator)? Also you need to consider the maximum size of the shark and what kind of space does it need so that it can be kept for life.