@Arthur Chu There are a ton of threads in here about the same as you are asking, your questions and more will be answered. As Ryan said, we have quite a few STR only communities with amenities and locations that are made for tourism and are zoned specifically for rentals. If you go outside of those, you're going to risk losing the attractiveness of why people come here. They want to be close to the theme parks and have a well themed house. Since we don't have ocean/mountain views or unique locations, the community should have great amentities (like Championsgate, Solara, Solterra, and Storey Lake to name a few) and also have themed bedrooms and a converted garage.
To address your saturation issues, yes, we do have tens of thousands of STR homes, but we also get over 70 million visitors a year. Finding the niche size will also be important, smaller ones (2-4 beds) will be competing against hotels, time shares, condotels, and townhomes and sometimes it can be a race to the bottom with ADR. So keep a clean home with amazing photos that is close to Disney and is well themed and you won't get caught in that trap.
Best of luck!