Something's just hit me that I think is worth bringing up. I was reading my description of Extended Yuffie Warping in my walkthough, and I've noticed that it may be possible to Yuffie Warp without Yuffie:
Step 3 of part 2. 
1) SET UP A 'GLITCHED' FILE
Before doing anything, you'll need to have 2 save file. One in which you have 
obtained the Highwind, and another in the Shinra HQ, before fighting Motor 
Ball.
1 - Load up the save file with the Highwind. Fly over to Midgar, and 
    *remember where you park it*. Now travel by foot over to Junon Forests. 
    Save your game here into a new slot.
2 - Now load up your other save file, and get into the Motor Ball fight. 
    Purposely loose this battle, so that you get a game over screen.
3 - Load up the first save file, and keep battling until you encounter the 
    Mystery Ninja. Defeat her to Yuffie warp to the Motor Ball fight. Defeat 
    Motor Ball and escape Midgar.
4 - Now head over to the *invisible* Highwind (remember where you parked it) 
    and then fly over to the back entrance to Mt Nibel. Before entering, be 
    sure to have Barret and Red XIII in your party (and NOT Cait Sith, 
    Vincent, Tifa or Cid).
5 - When you enter the back entrance of Mt. Nibel, the game will appear to 
    have frozen. Wait roughly 10 seconds to find out that it hasn't. Once you 
    have regained control of Cloud, leave Mt. Nibel back to the World Map and 
    save your game into a new slot.
You now have a 'glitched' save file, in which the game will not be taken to 
the reward screen at the end of a battle. Some really peculiar things occur 
when these parameters have been set up. For example, we can now trick the 
game into confusing the *battle ID* for the *field ID*....
2) ENTER INTO THE DEBUG ROOM
To make things quicker, you could kill off all three party members of this 
'glitched' file. Do that by first killing Red and Barret in a battle, escape 
from said battle, then swap out Red or Barret for someone (alive). Enter into 
another battle, kill Cloud, escape, then swap the alive character for the 
dead one. Save over this file.
1 - Enter into Mt. Nibel through the back entrance. Enter into a battle on 
    the first screen and die.
2 - Now load up the save file that you wish to warp to the debug room from. 
    This has to be at any point during the game *after* having obtained the 
    Tiny Bronco.
3 - Fly over to the World Map area just outside of Mt. Nibel (Rocket Town 
    side), and enter into a battle just outside the entrance. Defeat the 
    enemy to warp to the field map that you had died on. Note that you could 
    have won any battle on the world map and you would've warped to this 
    location, however you'll need a means of transport parked outside of Mt. 
    Nibel.
    *DO NOT* enter into a field map from this point on.
4 - Now fly over to Junon. What you want to do now is enter into a battle 
    with 2x Nerosuferoth (front row), and 1x Formula (back row). Keep fleeing 
    from battles until you encounter this battle (DON'T defeat any enemies). 
    This is battle formation # 65.
5 - Once you have fled from battle formation # 65 (2x Nerosuferoth and 1x 
    Formula), the game weirdly assigns the battle formation ID as the field 
    map ID to jump to on the next battle you win. So, defeat the next 
    encounter and you will jump you to field map # 65, which is the entrance 
    to the debug room.
    Enjoy!
Can anyone shed some light on this??