In a diorama of the Balin's Tomb the smaller scale would accentuate the environment, not the characters -- and as that set was just gorgeous, I'd buy it just as an empty environment sculpt. The characters would be just a bonus. Also, it would go perfectly with the Moria. So bring it on, pliz.
I'd get the iconic Cresting dio too. But whatever they do, I just hope it's always more than just character sculpts on a nondescript base -- which is one of my major gripes with the first piece of the line, and also a considerable problem with the second one. The two SW dioramas both have very iconic environments added to the character sculpts, and that's why I love them -- it's like owning a piece of those worlds.
I'm still surprised by how much I love the Space Slug enviorama, and hope to see that feeling recaptured in future pieces of the LOTR diorama line.