I really love the idea of Ursa being June. I think that, if you combine several of the previously stated theories, it's entirely plausible.
I can't see Ursa as a murderer unless she were defending one of her kids, especially Zuko. It's very easy for me to see Ursa and Ozai getting into a huge fight with Ursa admitting that Zuko is Iroh's. If Zuko is Iroh's, then Ozai is 4th in line to the throne. I've always entertained the thought that Lu Ten's death wasn't so much battle-related as it may have been an elimination orchestrated by Ozai.
For the sake of this scenario, I don't think that Iroh knows for sure about Ozai's hand in Lu Ten's death, but he has a feeling. For all we know, he's coming home to abdicate his claim to the throne as his position as first-born may have cost him his son.
Now, I'm not sure that Iroh knows Zuko is his son. Actually, I'm pretty sure he doesn't, and he might even believe that his fatherly feelings for Zuko are because he's a surrogate for Lu Ten. Of course, Ursa's not telling anybody as she knows that Zuko would probably meet with a fatal accident. But then, Zuko lives after Ursa leaves, so she must have some good stuff on Ozai that keeps her son alive. Why Ozai doesn't just kill Ursa is a mystery...unless, somewhere in that black heart of his, he really loves her. Hence, her banishment.
Ozai probably feels that Ursa (and, later on, Zuko) won't survive her banishment. Surprise! She learns to fight, becomes independent, and, in due time, takes on the persona of a tough, coarse bounty hunter. Now that I think about it, Ozai knows about June. Why else would he make the comment to Zuko about banishment being far too merciful? The tactic failed, not once, but twice. Zuko learns his destiny and joins the Avatar. Ursa becomes bad-a** June.
June's interactions with Zuko have to be guarded as she might endanger Zuko. Iroh's instant and (imo) intense attraction makes more sense. June's frown when she's laying on Iroh...consternation that he may blow her cover.
Yeah...it's speculation mixed with wishful thinking, but I can totally see this going down.
Meh...you've seen nothin' once, you've seen it a thousand times.Fantastic sig by DragonSpirit - Thanks