Leslie Judge said:

I was thinking about the Vader killing Anakin issue.

If I'm correct then in the OT nobody evers says that a Jedi can't teach more than one padawan, so Obiwan could have had a group of students. He even says '...who was a pupil of mine...'

Yeah, no one ever says "padawan" in the OT, so I think we're safe on this one.

If Vader's name comes up earlier so we know that a Darth Vader exists somewhere and he is a former Jedi who turned to the dark side, then Anakin could be sent after him alone or with a few other Jedi to capture/defeat Vader.

If we see Anakin go on a mission at some point in the movie and later Vader comes back telling Obiwan that Anakin is no more then only Obiwan knows what he really means and who he really is (if he can sense his true identity), we don't.

During their conversation/fight Vader could refer Obiwan as his former master, so Obi wouldn't sound such a liar in EP IV.

Of course this means that Anakin should have turned to the dark side earlier and that he is good enough with the Force to hide this little fact from the other Jedi.

This is what Blackhawk meant when he referred to the Dread Pirate Roberts phase of this discussion several pages back. I, for one, am not opposed to the idea. I think it could really work if done well... but I fear it being a total train wreck.