The choice of does Mexican work is a much more fundamental question, it be a solo site place, an upscale chain, or chevy's. That question I am not sure demographic wise if its a good fit or not, but on property they already have Steak House covered, the have Italian covered, and moder/fusion covered, so going with another separate offering i can see being a good choice from a marketing perspective. Arguably you could have gone with an Asian themed or even seafood type place, but I don't see Mexican being all that big of a disadvantage.
As to unique vs chain, I am not sure of the benefits of going the totally unique route. What is the reason that WDW would want a restaurant at one of their resorts that people wouldn't got to in other cities/tourist locations? Disney has their character/themed dining experiences that serve this type of experience. I wouldn't go to a restaurant in NYC that has a bunch of furries hanging around and interacting with guests, but we will do that at Disney bc its the Disney characters we know and love. But here we are talking about a restaurant within a Hotel Space, and a non Disney Hotel at that. This is the Hotel that Bonvoy members spend their points on, and that conventioneers will be at. If anything for that demographic I want restaurants that people have a sense of familiarity with. We did Don Shulas on our trip to Chicago, it was great, lets eat there type of decision making. For anyone going with a family, especially with young kids, when we are sitting down after a long day at park, we aren't looking for a "Unique" restaurant experience just hoping all of us, and the kids will like.
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