You know a Defenders plot that would interest me? I just thought about this...
The core Defenders (Hulk, Strange, Surfer, and Namor) get pulled into another dimension for some reason and along with them are more relatable Defenders Beast, Ice-Man, and maybe Gargoyle. Also, the kids Loa and Skaar.
This dimension puts them in situations where the core Defenders must face their dark sides and cause a lot of problems due to it (Hulk's hate and rage, Surfer's alliance with Galactus, Namor's craziness and pride, Strange's connection to dark magic/Zom). It becomes a bit of a war between the four.
Beast, Iceman, Gargoyle, Skaar, and Loa will have to rise up and confront this and bring each of the core members to their breaking points and help them deal with their demons. Make it dangerous, maybe Gargoyle giving his life, and in the process young Skaar and Loa can find a romance and learn to come out of the shadows of Hulk and Namor.
I don't know... something like that. Do a bit of a Planet Hulk approach to them all for a year and build them up and then return them to the core 616. It was an idea that popped into my head and with Beast, Ice-Man, and Skaar... I'd be game to read it. Just a thought.