IoA is in a difficult position because there isn't a whole lot you can do to expand it. The two areas to work with are replacing Marvel and replacing Lost Continent.
My first suggestion for replacing Marvel was a Sci-Fi land so you can replace Spider-Man with Transformers. Since that ain't happening I'd suggest DC. Spider-Man would be replaced by a Batman Archam Asylam ride, Hulk would be replaced by Superman, Storm Force is replaced by The Flash and Dr. Doom is replaced by The Joker.
Lost Continent is fairly small now that Harry Potter took over most of the land, however it does have two attractions that are a decent size. My suggestion? Middle Earth. Yeah, it's next to Harry Potter, but LOTR/The Hobbit is a different beast. I'd convert Posiedon into a Mines of Morria roller coaster and the Sinbad theater into Hobbiton, which is a walk through attraction with themed resturants and shops. I'd also include the Prancing Pony themed eatery.
For Middle Earth, I would convert the area near Mythos into The Shire, which is really just an area you can walk around, and then where the Mystic Fountain is, that would become Bree, with a Prancing Pony and a few quaint little shops. Then, the building encompassing Posideon's Fury would be expanded and joined up with the Eighth Voyage of Sinbad building, to make one huge building with would house 'Lord of the Rings: The Journey', which can be accessed from Bree.
Lord of the Rings: The Journey is a dark ride, similar to Soarin' at Epcot, but on a much bigger scale. The ride combines screens with real sets, and the seats are like Soarin', but they move around a track, and are suspended from the ceiling (I hope I'm making sense!).
The ride begins in Bree, where you are picked up by an eagle. After gliding over The Shire, Rivendell and Minas Tirith (via the screens), the ride takes a dramatic turn when the eagles take you over Mordor (which would be a giant real-life set), and the Eye of Sauron tries to destroy you. The room would be heated, to add to the experience, and lava would blast up to your dangling feet. But then you escape and win, and that is the end of the ride.
I think that would be amazing for a ride. The only issue is it might be too similar and too near to Harry Potter and the Forbidden Journey, but I'm sure people would still flock to ride it.
Of course the other option is to convert Toon Lagoon into Middle Earth. Popeye and Bluto's Bilge-Rat Barges could become 'The Shire Barrel Boats', and then the area around Me Ship the Olive could become The Shire. Then the whole area where the shops are could become Bree, and Comic Strip Cafe could become the Prancing Pony. Then Dudley Do-Right's Ripsaw Falls could see a massive overhaul and become a huge replica of Minas Tirith, and could encompass the 'Lord of the Rings: The Journey' ride I described in the previous paragraph.
What do you think? I realise both options, particularly the latter, are very ambitious, but they are certainly not impossible. I think a LOTR land would attract a lot more visitors than you might think.
