The immolation scene

Why: It makes no sense in my mind that Obi-Wan could stand and watch Anakin as his body is engulfed in flames. Firstly, I don’t think a Jedi would allow for another to suffer a death so horrible, even after the atrocities that person had done. Watching someone, an old friend, burn to death requires for someone not to have a heart. Secondly, Obi-Wan knows why he’s there: to kill Anakin. Therefore he should have no problem taking his lightsaber and beheading Anakin or stabbing him through the heart. This would ensure his death and at the same time spare him all the horrible suffering.

I also found the scene of Anakin burning up as uselessly violent. It doesn’t look or feel like anything we’ve seen in Star Wars before, and it doesn’t look like it belongs in Star Wars.
Obi-Wan also picks up Anakin’s lightsaber in a really meaningless way; he’s practically in mid-sentence as he’s picking it up, putting very little focus on an event that is regarded as almost mystical in ANH.

Also, Anakin is obviously alive when Obi-Wan leaves him. It made no sense to me that Obi-Wan left him alive after all that. If he was there to do a job, at least do it right. Obi-Wan must have been blind and deaf if he didn’t see that Anakin was still up and about.

Lastly, I felt the dialogue to be a little disappointing. It could be tweaked up to sound better.

Therefore; the immolation scene needs some work.

How: If Anakin is to die slowly, then he should at least be in a place where Obi-Wan can’t reach him. This would eliminate a lot of questions about whether or not Obi-Wan has a heart. If my previous idea is implemented, it would take care of that problem easily.

Secondly, the dialogue could be a bit better to feel a bit more epic and tragic. It could go something like this:

FAN IDEAS NEEDED

Now, as for what happens to Anakin, well, he lets go of the ledge that he was holding on to, and is seen falling off, into the lava. This proves to Obi-Wan that he is officially dead. Of course, in the scene where the Emperor finds him, we see Anakin totally burned, hanging on to a small rock formation or something in the middle of the lava river.

The last thing to think about is how Obi-Wan would get off the platform that I mentioned in my previous idea, which was supposedly surrounded by lava. The best idea that I can come up with is that one of those floating droids passes by the platform and Obi-Wan just hitches a ride with it.