I cleared the Realm Of Memories today, pretty much in one sitting.
For those of you who don't know (though I don't think it's a spoiler since it's in the trailer for the game), the Realm Of Memories includes areas taken from A Link To The Past, Link's Awakening (non-DX), and the original The Legend Of Zelda. They are modified, of course, but I found Link's Awakening very neat (it was a bit more fresh in my mind, having recently finished the DX version on the 3DS VC), as a good amount of the landscape was true to the original, but now being able to see more than one "screen" at a time was interesting, and with multiplayer, it reminds me of that Castlevania: Harmony Of Despair game on XBLA and PSN.
I don't know how feasible it would be to map the Realm Of Memories from the Anniversary Edition version, but I've always felt that the GBA version of Four Swords could have been attempted. Sure, most of the main stages are random, but from what I've seen, I can't imagine that there are too many random parts. Certainly there could be a large number of overall permutations and combinations, but there might only be a feasible number of map segments that could be mapped out.
Considering that Four Swords is one of the least played games in the series, now reintroduced to a whole generation of 3DS owners (at the moment, not very much, but still!) I second the request to see Four Swords mapped somehow.