How is a remake of a remake different from simply remaking something a second time?
One thing I like about remakes is that it allows you to use newer Pokemon in older locations. For example, if there hadn't been remakes, Kanto would've never even seen Gen III Pokemon.
It also allows you to experiment with new game mechanics that didn't exist before. For example, abilities - Pokemon Tower is completely different in FRLG than in RBY because of Gastly's line having Levitate, and, maybe it's me, but I tended to Dig my way through in the originals.
Gen III minimized the impact of the new types on Kanto. It has no Dark-types, and its only Steel-type isn't very defensive and didn't learn any Steel-type moves.
However, Kanto does have a few Fairy-types which might be interesting to see in a region designed (and balanced) when it didn't exist. And, if HGSS is any indication, they will add in the level-based evolutions (other than the location-based ones), adding Sylveon and Umbreon. Plus, Magnemite learns offensive Steel moves now...