Here's my reasoning: First off, the DS is oddly wired to better handle 3D applications. After seeing titles like Ninja Gaiden: DS, Nanostray 2, and other primarily 3D apps, it could easily handle DF or Arena.
Yes the storage cap on the DS carts is a bit off-putting, but the textures and whatnot could be toned down to conserve space. As well, movie compression has been greatly improved, so the movie files on the original disks that used to take up like 60MB could now take up like 5kb. If not the movies could just be made still frames with text.
I think the predominantly mouse driven gameplay of DF would work great on the DS screen (Think Metroid Prime: Hunters)
Top screen could just be a generic map display or other info.
I think it would be a good way to get a bit more out of the old titles, without people complaining that the games look dated, since the DS's graphical capability isn't that far above these games.
As well, it would fill that nice little RPG hole that the DS has, as it lacks proper RPGs (too many tactics games.)
One game that comes close to this idea is Deep Labyrinth. Though it's more of a Proof of Concept, since the game stinks.