It is pretty obvious that Enel is going to come back into the story at some point, probably a lot stronger then he was before. He probably won't show up in this arc, but I do think his return should soon. So because of this, and the fact that I have been rereading one piece, I think there are a lot of questions yet to be answered about this character that should be shown when he come back. For one, he is the only character in Skypea without wings, and instead has that drum thing on his back. Did he originally have wings and cut them off? Or did someone else cut them off when he was young? And speaking of him being young, Oda has never gone into any of Enel's back story, in fact he hasn't even drawn him as a child. From what I've seen Logia fruits are hard to get and often are obtained by either the government or powerful pirates. Enel's is said to be one of, if not the most, powerful of the logia, so him just finding it randomly seems suspicious. Also, if he is back on earth, has he run into people more powerful then himself? Even with his big ego Enel doesn't seem that stupid, so he probably will have to accept the government is more powerful then he is. And the final question, is he going to be working for himself or someone else? I think it would be an interesting twist to see someone being the Boss of Enel, probably be very funny too. I'm looking forward to his return, and hopefully some back story about him.
You know, I was actually thinking about Enel just the other day as well, though I will admit he was largely involved in a my theorizing who the seventh Warlord is and not so much as to Enel's backstory. Regardless, I absolutely believe Enel will return to the story somewhere down the road, which isn't unfounded as Oda has most recently introduced Bellamy and Sabo, both largely believed to have served their purpose in OP and both widely assumed dead, though many will fervently deny this case for the latter. Curiously, both these characters were never explicitly stated to have died, yet both returned alive (though it didn't look promising in either case)...I wonder if that applies to any cold-hearted harpies we recently came to know? Arguably the rest of the currently known Warlords, from Buggy to Kuma, and even the former ones like Crocodile and Moria--who've all played a significant role in other arcs or plotlines--are guaranteed rebirth within the NW saga. Even someone, who had been guaranteed capture by the WG, a la Bonney, has resurfaced in the NW under mysteriously interesting circumstances. In other words, Oda reintroducing previously introduced and involved characters isn't out of the question, especially for someone as powerful, egotistic, and farseeing as Enel. For me, Enel fits no place better than the final unnamed Warlord. Someone of his caliber--strength, ability (both DF and otherwise), intellect, ambition, mercilessness--would certainly be the sort of intimidation figure the WG would wish to have 'on their side'.
Now Oda could certainly be reserving the name of the final Warlord in order to keep us guessing as to who he/she may be, especially for if and when he introduces this possibly new character. Indeed, I have had difficultly gauging who else previously involved in the series pre-time skip could taut enough repute and accommodating value (power, ability, knowledge, etc. (though it would be interesting how 'valuable' Buggy has become in the WG's eyes)) to earn particular singularity among the WG acknowledging the Warlords. Therefore, Enel seems only logical to fill this void. He is beyond powerful, intelligent, intimidating and fearsome. He is, though heavy-handedly stated, God-like. For all intents and purposes, I believe this is how Enel will reappear into the Opverse. If not, any other capacity would work just as well.
I have said this years ago and I will say it again Enel WILL come back and would be a shichibukai. The recent fact that the seventh shichi was kept a secret just made my theory a little more plausible. Just think about it, if the last spot would be for a new character, Oda would have given us at least that persons name just like the other new Admiral. But he didn't so there's a good chance that it's an old character and nothing would fit more to it than Enel.
I'm just gonna restate my theory here. Enel after going to the moon got bored and disappointed as there's nothing spectacular to it outside of his robot minions. He doesn't want to go back to sky island as he feels that it doesn't fit him. But he noticed something strange back on earth. He saw a long red vearth cutting across the sea (red line). He finds it more interesting than the dead land of the moon so he decided to check up on it.
As he went down back to Earth, he saw a city (Marijoea) and went straight to it. He then meet the Gorosei and the Admirals. After a little scuffle Enel realizes the strength of the Marines but at the same time his God like tendencies just push him more in conquering this world.
He decided to take things slow as he thinks of a way to overpower the whole government and the best way to start things off is become a Shichi. Lots of people have taken a seat for their own purpose (Croc, BB, Dofla) and the WG knows this applies for Enel as well but he's too strong not to be on their side so they just went along for it.
A Shichibukai? Really? Why would God serve under man? Not only does being a Shichibukai not fit his style, Oda has already given us hints onto who the newest Shichibukai is and it doesn't fit with Enels story. The Shichibukai is the one who cut off Z's arm years ago and killed the admirals crew 4 years before the current story, of which Enel was acting as God at this time.
Enel just isn't the type to even pretend to follow someone else. He is also unknown to the World outside the White Sea, so because no one knows him, no one would fear him. Even Blackbeard couldn't become one until the world was told that he captured Ace.
Yes, 'God' serving beneath 'Man' seems a bit farfetched. However, are we sure that one of the known Warlords weren't the one to severe Z's arm off? Crocodile? Moria? Doflamingo? Mihawk?! Any of these could have knocked severed an arm and killed his family. I'll admit I'm not aware of the timeline between the movie and canon story, so clarification would be much appreciated if I'm wrong about how a current Warlord could be the culprit.
Nevertheless, Enel would be one of if not the only character who's already been involved in the story capable of earning such high honor of mysteriousness as a Warlord. Of course, we're only speculating and not until Oda introduces the last Warlord will we know for sure.
Enel is in space simply because he's too much of a character for Oda to handle and get the story done right atm. I expect he'll make his entranced in the NW sometime when the SH are strong enough to not be KO'd instantly. If he was the last warlord it would be a nice twist.
@ xiaoxiao, yup that's pretty much the flaw on the theory but I still firmly believe it would be him. Enel thinks he's god but he's also smart enough to know when he's outgunned. He did not even dared to go back to Luffy was after he regained his consciousness. He's like "screw all of you, I'm going to the moon". Though I do believe that he and the WG had a special agreement just to gain his service to a point that he's not a shichibukai working for them but an equal partnership or so Enel would think.
Being an unknown guy would not matter much, he could just do what BB did and he'll be instant celebrity. I do not know much about the Z film though so I don't know about the hints Oda gave.