I know about the pausing (love this in friendlies) and that fighting zelda makes its much quicker, but I'm wondering if there's anything I can do to avoid absurdly long transformations. From what you said, I'm assuming it depends mostly completely on the Wii itself? I was thinking stage played a decent factor, because I remember someone saying something about Lylat lagging their transformation. Anything else specifically. I also remember my friend saying that he saw someone transform faster after the first time, but from my experience the time it takes is random no matter how many times you've transformed.
The majority of the time it will take to transform depends on your Wii disc reader. So take care of your Wii. But as I said before, stage information and other things will factor into your transformation. Instances where other codes of info will clog up and out prioritize the command to transform, like new scenery frames in the background of the stage, an item spawning, stock's changing, opponent respawn.
Small things, the entire game going on in fact, is all receiving data and that's when you hear your Wii click and what not while reading the disc. Try transforming during a clean reading, listen to it.
(Example of 1 match-I just tested)
If Player 1 is Sheik, Player 2 is Zelda and Player 3 is Sheik for example.
Lets say Player 1 Transforms, the time will be cut considerably while he transforms into Zelda. When Player 1 Transforms back to Sheik how ever, even though Player 3 is already Sheik, it takes more time then it did when he transformed into Zelda for some reason, only slightly by my count.
Now with Player 1 as Sheik, Player 3 as Sheik and Player 2 as Zelda, the time it takes to transform to Sheik for Player 2 becomes the same count as Player 1's Down+B into Zelda.
Now all Players are Sheik BUT the transformation Time of turning into Zelda was Kept even though no players were Zelda.
The Player with the lowest port always transforms the quickest by priority. (if all players transform at the same time) Or even in general it seemed that way. So it is always better to be Player 1 if you ever find yourself in a ditto match.
In all cases transforming to Sheik took longer then transforming to Zelda, which is good I guess.
(Example of 2nd Match)
I went to the same level. Player 1 is Sheik, Player 2 as Ganondorf.
The time it took to transform from the previous match, stayed. (Personally, it was off by 1 count but it was still considerably low) So that would prove my theory of transforming previous to all matches would lessen the time in future fights, at least if you're fighting on the same level.
(Example of 3rd Match)
new level, new opponent. The time to transform seemed to stay the same as the 2nd match, Taking only a little longer to get to Sheik by 2 counts though.
summary: Transforming into Zelda takes less time then transforming into Sheik. Player port with the lowest number count (1-4) has priority over the rest. Another Zelda and or Sheik in the same match will cut transformation time down. Pausing will allow the disc to be read and upon un-Pausing transformation is faster. Previously transforming on stages you plan to fight on seem to cut down Transformation time.
Stage scenery, item spawn, or other data input during a match may result in longer transformation.
Overall it is situational, and dependent on many factors but those are some things to consider when Transforming.