I liked the setup at Pimlico, but it's not as easy to get to/from and parking was a nightmare. Merriweather is not a bad idea and if you decide to do a stadium, consider taking a page from the Vegoose festivals in Las Vegas. Even though stadiums are not the best locations for festivals (as others here have pointed out), it can work.
One more gripe...with the right line-up you can draw from just about anywhere in the country. BUT it HAS to be promoted much better than this year's festival was. I live in Baltimore and RARELY saw/heard ads for the festival anywhere. I knew about it mainly because I pay close attention to the music scene around here. I had friends come down from New York who told me that they never saw a single ad for this year's festival and that if I had not told them about it, they never would have known that it was happening.
I know there was some limited national exposure from several magazines, but you really could have drawn a lot better if you had constantly peppered the east coast markets in the months leading up to the show.
Other than that, you did a great job. I appreciate the effort you put in to make it happen and I look forward to next year.