I am going to deal with two separate parts of your posts separately because there are really two separate issues..
- An exterior Epoxy
- A basketball surface
There are a lot of very good epoxy products on the market that can be used in circumstances where an interior finish goes past the threshold and extends outdoors for a small area. I am sure there are some, that would argue with me, but I would not personally use an epoxy floor coating for a 100% exterior application. I would however take a look at Legacy Industrial's Polyurea based products.
That said, using a coating for an exterior sport surface has certainly been done but is, in my opinion, a dangerous option for the 'general public' If you don't add anti skid you have an ice skating rink and if you do... well OUCH.
Companies like Connor Sport Court and Swisstrax have been making modular sport flooring that is idea for this type of application. If you want a 'high end'
sport court I would check them out.
If your looking to accomplish the same thing on a budget the Sport Court product sold as Tylon, drain tile or TopDeck is very similar to the sport surfaces and works incredibly well. Make sure you get the one that says drain and sport.
http://www.garageflooringllc.com/motormat-garage-floor-tile-from-sport-court/ for slightly higher end but still less than a true 'sport court' check out
http://www.garageflooringllc.com/premium-sport-drain-tiles/
I am fairly certain that Racedeck has a series of options that will work as well