@Nemispelled Thanks a lot man, your posts here have been great, I can see both sides to this but I personally agree with you.
It literally would have changed nothing. Natsu wouldn't have discovered he was END, and so he would still be saving Igneel's magic power for Zeref. It would be a waste to use it against any of the other Spriggans before that time. Natsu purposely held back on using Igneel's power against both Brandish and Ajeel, so he would unlikely be using them against any other Spriggans - especially since he can arguably take them down without it. When he finally faces Zeref, Zeref would reveal that he is END...and we're back to square one. And if we're saying that Natsu takes on Zeref with a bunch of his friends, then it wouldn't only be Happy convincing him not to do it.
First off, my bad, when I said that he could have used it to destroy Sprigs I meant in a scenario where they run into August/Irene (and maybe DiMaria due to timestop), they were pretty much screwed the last time they ran into August and it's looking like August and Irene are going to require multiple powerhouses to be taken down.
Destroying Zeref is certainly a tough thing, though I believe there may be a couple of alternatives:
1) A plan by Jellal
Jellal stated that his (and CS's) goal is to destroy Zeref and we know that Jellal is intelligent and a magical prodigy (the only people who know more magic being Zeref and August), I think it's incredibly likely that Jellal has come up with a theory/plan that might be able to kill him.
2) A plan by Mavis (This might be more likely given what she recently said on the battlefield)
Mavis is the only other sufferer of the curse that we know of so she
should have some idea of how to kill Zeref, at the very least she should be able to come up with some theory. IIRC she was killed by Zeref's curse because he loved her more than she loved him, maybe the reverse is possible?
With the above being said, there likely isn't another way (or at least one we can predict) to kill Zeref and it's this that makes me think Natsu's plan was far too hasty as now they're in a scenario where they're relying theories to kill him when Natsu had something that had a decent chance of ending him. I want to be clear though, I'm not saying that Natsu is at fault for what happened when Happy (sigh) dragged him back, I'm just saying that he was too reckless IMO and that his decision cost him. He couldn't have known what would happen but it was foolish to solo Zeref in the first place given that he only knows one part of Zeref's skill set.
I don't buy that removing Zeref from the battlefield is a bad idea. First of all, Zeref is the strongest opponent on the other side. Any supposed anger-boost isn't going to outweigh this. Even if someone was more tactically apt, the whole reason they're going for Fairy Heart is to allow Zeref to take on Acnologia. Secondly, Zeref has had 400 years of experience and is actually portrayed to be a genius. Who exactly is more tactically apt than he? Even if they were, it wouldn't be by ridiculous margins. Also, it's not like news of Zeref's death would have reached everyone immediately. The Spriggans that were defeated would still have been defeated, and unless Irene sensed Zeref's death universe one would still have been casted.
First of all, Zeref hasn't even entered the battlefield so had Natsu succeeded it wouldn't have physically affected any of the battles. As for Zeref, his tactics really aren't making sense, UO put him in a perfect place (S8, Historias and 1 mil fodder) but Alvarez is actually managing to lose? Why didn't they send someone like August in and keep Neinhart and Invel out of harms way? About the Fairy Heart bit, I'm not questioning his motive, just his tactics.
I'm not sure if there is a better tactician than Zeref in Alvarez but I'd assume that Invel must be a decent strategist given that he's the chief or staff, though this is the same Invel that knew he was the reason Mavis was trapped and then went out anyway
.
Had Zeref been killed then Invel, any of the Black Carpet and possibly Irene (via sensing) would be able to pass the message on and given how he's worshiped by the S12 and Alvarez as a whole it would almost certainly cause them to fight much harder.
Even with this all being said, I can see both sides of the argument, I just feel that Natsu's impulsiveness (which was displayed perfectly in his plan to solo Zeref) is a quality that would be awful for a guild master. The results of the plan don't really matter that much IMO, but the fact that he just went there without telling anyone is a huge negative in my eyes,