Yea, I might go ahead and do that later.. it just kinda seems odd to post a thread about a run that I'd rather see someone else do.
In any case, looking things over, going Beast -> Nature -> Sun wouldn't take any more time than Beast -> Sun -> Nature, barring the possibility that one of them would take an extra turtle trip (I'm not sure which, though.) I'm not sure if using Nature form to climb the left side of the Sun temple would save any time, maybe there's someone way better than me at fast briarhopping though. I'd like for it to be possible just to make the run more interesting, though. In any case, a segmented route would probably go something like:
1: Start to song cave to saving before the "boss" that gives you Energy form
2: Energy temple up to the save before the boss
3: Leave energy temple, go through open waters and Mithalas to the save point outside the cathedral
4: Mithalas cathedral to the savepoint at the beginning of the area with all the currents
5: Leave Mithalas (get beast form), pick up the ancient turtle near it, head to the savepoint before the Kelp Forest boss, getting the Kelp Forest turtle along the way.
6: Get Nature form, take the bulb to the turtle, then the turtle back to outside Mithalas, head up to the Veil, get Li and save at the first Sun Temple crystal
7: Either climb the left side of the Sun Temple to the boss or do it normally (possibly saving before the boss if doing normally, if so this would make an 8th segment, but let's assume we don't..), get Sun Form, leave through the exit in the boss' room, take the nearby turtle back to outside Mithalas, save somewhere on the way to the Abyss.
8: I'm not sure which route is fastest through the Abyss to the Sunken City, but suffice to say one should figure it out and do it, go through the Sunken City, save before the Golem Boss.
9+: Save as few times as possible throughout The Body (the crystal is kinda out of the way), but realistically it'd be hard not to have to do it a couple times. Definitely save before the final gauntlet, after getting Li back.
10: From getting Li back to the save before the final boss.
11: Final boss.
Something like that sounds about right.