What I'd love to see is if it were taken to the next level entirely and just have some kind of FF1 roguelike almost with randomly generated dungeons. Maybe even just one huge dungeon that you just delve deeper and deeper into with "town" type floors along the way. You could have "power levels" associated with equipment making it less likely or even impossible to generate end game gear in the beginning and more likely as you go deeper. I'm well aware of how much of an overhaul that would be and the ridiculous amount of work that would entail but it seems like it would be totally awesome.
The Dragon Warrior Randomizer is able to generate new maps programmatically. While such a thing would be possible for FF1, it's much more challenging because the game is just a lot more complex.
I think a lot of interesting things are possible, though. One recent suggestion was simply to shuffle 2F of Castle Ordeals, so all the teleporters go to different places. That would be neat having to re-solve that floor each time.
We have EVEN MORE themes now, but some old ones are gone...