I honestly don't think DCA needs its equivalent of a $300 million dollar movie, a AAAA video game, or a billion dollar ride. It's putting too much pressure on a single ride based on a single IP to fix an entire park. Disney parks seems to suffer from the same problems of overthink and scale as their film division, when they could probably improve the park easily by using existing technology to build cheaper rides that appeal to their core theme park audience rather than every human on the planet.
So instead of trying and failing to build a ride that fits the Platonic ideal of what an Avengers ride should be, just build a good coaster. Don't break the bank on it. Then you can build a short boat ride, or a dark ride in Hollywoodland, or some flat rides for Grizzly Peak. Just do something, make mid-size yet effective bets that are still draws and don't purport to be some magnum opus of themed entertainment.
Basically, they should just do what they did in 08-12.