Personally my 2 favourite FF games are hands down FF8 and FFX, simply because of their unique character progression systems. A mixture between the GF system of learning and equipping abilities combined with a sphere grid-type system for stat raising would be awesome (though likely sounding better than it would turn out). I have yet to play ff13, so I'm not sure how it works, but BRING BACK WORLD MAPS!!!!!! Although with the feel of FFX and it's pacing, the lack of a world map was missable, but FF12 felt like playing a mmorpg, running (and running and running) across the world to kill monster x, running back to claim reward, next quest running all the way back to almost the same area to kill his twin brother, etc