Something like Six Degrees disc 2 would be awesome, like a "mini" concept record that doesn't really tell a story or have lines that represent character dialog (those kinds of albums are cheesy), but is united by an overarching concept and several common themes anyway. I'm also thinking along the lines of dredg's "El Cielo"... something a little less than the full-blown rock opera prog metal is drenched with, but still a bit more than the usual "theme" albums DT do.
I really don't see what's so bad in story-based concept albums.
IMO, if you have a good plot, or even a basic story background, the album could turn out pretty good.
For example, Kamelot's "Silverthorn". I think it's great, and it's totally story-based.
Also, I don't think that SFAM's story is bad, unlike some of the members here.
I'm a fan of concept albums generally, and I really think that if DT12 turns out to be a concept, it would be great