I guess that high-quality 2D (which means no sprites) could be an interesting way to present VI, as it would be true to its roots. But I think that 3D allows the developers to put a lot more detail into the world, and make it a lot more believable.

I know someone will disagree with me on this, but look at how beautiful some of the locations were in X and XII. In XII, especially, the Phon Coast is spectacular. But one would lose that sense of grandeur and scale in 2D.

However, as I've mentioned before, I don't think VI should be remade for a portable system. From what I've played, I think it deserves more than that, and only a remake on a next-gen console would be appropriate.