An ending without the lion turtle

Avoiding the energy bending asspull.

Aang solving it in his own way could just be to wait out the comet or just keep ozai under a giant wet rock as prisoner.

All the airships were down. What was ozai realistically going to do at that point, he was stuck in the bay on his own.

Zuko takes over the fire nation because azula loses her mind.

Book 4 can then be focused on kicking the fire nation out of the earth and stopping those generals still loyal to ozai and willing to fight, etc. some elements of the comics.

If you really need to take away his bending then chi blocking/bending could be an air bending specialism like the others have metal, lighting.