The problem with making a DS remake is that the DS has yet to prove it can emulate the detailed graphics of a game like FFVI or CT. I'm concerned a VI remake on DS would actually be a graphical downgrade as a lot of detail would be lost in the backgrounds and sprites. III and IV have archaic graphics that were great for their time so having less detailed graphics for some things is actually still an improvement over their 2D incarnations.

While VI may be showing its age and in the era of 2D sprites its no Chrono Trigger, its still a game that utilizes a level of detail and scale in its design that I find it very difficult to believe the DS could pull it off, hell I'm actually speculating whether the PSP could make a true remake without modifying or creating some low grade concessions to make it work (human character models only used for cutscenes while in game is restricted to chibi form akin to the original, showing a smaller portion of the field/dungeon map during gameplay, Chibi sprites for battles or possibly cutting down the number of characters to three or most likely go the DS III/IV route and lower the number of enemy sprites on the field you can battle). To be fair, if they did remake VI they may have to redesign the game just so it can have high quality graphics and minor load times at the same time. Doing a true port on a handheld may result in them downgrading a lot of the quality of the original. To be fair, I feel FFV may suffer from a similar problem.

Ultimately, choosing the console to release such a game is going to heavily impact the quality of the title.