During Sozin Comet Iroh created a fire circle just by breathing and later with little motion of his arm he transformed this fire in a fireball floating in front of him. He never showed this technique/ability before. So, I have a reason to think that Sozin Comet also affect skills, maybe the amp is so great that some impossible techniques can be done because the bender is extremely more powerful.
Jeong-Jeong created the wall in "The deserter" but the boats stopped before they hit it, so we can't say that it would block them, it could easily only put them on fire. The only time that it moves tanks is during Sozin Comet. I still don't think that he can put a wall that easily as you assume, but let pretend he can, there is no way we can know how large and tall it would be, it's plausible that with the motion of his hands it would create something as large and tall as a human being, no fire bender has ever created so big wall as you want with a single gesture. Azula has blocked a wave made by Katara, but that take more time and movement that what you are implying. Zhao passed through because he fire bended, as Azula can do it too if she wants.
Kai took a direct hit from her and didn't die. Tenzin took an indirect one and continued to fight. Druk has no feats, we don't know how durable he is.
Ok, she invented the metal-bending but we can't give her all feats of metal-bending because of that. Also, "earth jumping" is different from "metal jumping", with earth your jump goes high depending on the amount of earth you dislocate in the form of a column, with metal it depends on the material "flexibility". Toph can be a great bender but the material is a limitation to her. Again, no feats to back that claim and you are assuming that Nyla and her can jump a considerable distance.
You still fail to point out how your team can react fast enough to avoid Appa when nobody has done that before. Appa is more durable than anything that P'Li has ever shot. He is using his armor that blocked multiple fire attacks without problem. It's difficult to hit Appa. Azula can block P'li as Zuko blocked CM.
Sure some have blocked her projectiles but also she hit, pinned, disarmed several fire nation soldier, earth kingdom soldier, Kyoshi warriors, fire nation separatists (comics "rebound"), Katara as well. The thing is that she can hit multiple targets with a really fast attack, this will force your team to take a defensive stance. She can hit Jeong-Jeong faster than he can raise his wall, so he continues the motion he will die, also, P'li doesn't have a defensive movement and has little to no reflex feat, and she can't shoot while in movement and she will need to move to avoid Mai attack. So, with Mai attack we'll have the window to Appa blast you all out of the platform.
Azula can use her lightening as well. In the comics "The search" she uses it as fast as Mako. That is one more thing that your team will need to be concerned with.
I think that a made clear that my team has more chance to attack you first but i'll leave it to the voters. I'll assume that your plan worked and show its flaws.
So there is this fire wall coming at me, Jeong-Jeong, P'Li and Amom are behind it. Nyla and Toph are way behind in the stands. Suki is alone in the lower level of the platform.
My team is behind the wall hide from your team because the firewall blocks their sight. So we jump on Appa and fly low to avoid your attacks and try a sneak attack. As soon we do that we spot Suki by herself. My team can easily take her in inumerous forms but the easiest one is Yakone bloodbends her throwing Suki in the water, Azula follows electrocuting her. One less, five more to go. No other member of your team can see it happening.
Now, moving on. Ming-Hua and Lin can go spiderman in the middle platform, below your team, they can cover that distance very fast. While they do that the others still on Appa. Now there will be another coordinated attack. Appa appears flying while Mai and Azula shoot drawing the attention, and from nowhere (or anywhere: side, behind, top) Ming-Hua and Lin appear. Ming-Hua can kill P'li with her tendrils that pierce steel, freeze her head like Katara did to Cm or slap her out of the platform, we know how fast is Ming-Hua when she get her momentum, so there is no way to P'li avoid it. Lin metal cables will restrain Jeong-Jeong in a way that he won't even see it coming, without his arms he can't do anything, so Lin can drop him on water or let him useless on the ground. Once one of them hit the water Azula electrocutes. Yakone will be there to block Amon, Yakone is a stronger bender that Amon, also we saw that a much weaker bender (Tarrlok) slow down Amon with his bending, so at least it's what will happen giving enough time to Mai projectile hit him and kill. Toph and Nyle can't do anything, they are to distant and Toph can't see anything.
At last we are going for the stands, 6 vs 2. Appa alone can take down Nyla as he has done before while the other can gang on Toph. She is good but not that good. Or Yakone can easily blood bend her and we kill her before we take Nyla.
@lunacyde That's it. In any case the fight will take less than 5 minutes.