On anime adaptions:
You could probably fit Digital Devil Saga into 26 episodes relatively easily, though you would probably need to exclude the various bonus bosses and sidequests. Nocturne, given its minimalist story and small cast, could probably fit in 13 episodes, but it might require a little rushing and sticking to the "vanilla" story, which means ignoring the Amala sidequest. Strange Journey you might be able to do in 13 episodes, but it would require cutting the sidequests and a lot of the fat in each sector (for example, Sector Bootes requires you make three, different visits to the Palace before you can fight the boss, and the events could probably be compacted into one visit instead).
A Raidou anime could also be fun, and maybe let us see the demons be used in a more "mundane" way in the sense of solving crimes and cracking cases, but I think they should make an original story for it, rather than adapting any one game.