I’ve been doing a rewatch/read of the series this year and I’ve recently been looking a lot at the Full Body Armament Haki users. I’d say Vergo was ridiculously strong with it but it didn’t do much for him in the end. I think he lacked the speed that other characters have, and relied on brute force.
Another Full Body Armament Haki user was Pica, but this technique did basically absolutely nothing for him as Zoro had no problem cutting right through it.
I’ve seen some people say that Full Body Armament Haki is kind of useless, you only really need it in the part of the body you’re using to block or attack. Reasonably we can assume that it’s stronger if you focus it in 1 area.
So I was thinking about how Luffy essentially makes full efficiency of “Full Body” Haki in Gear Fourth by only using it in the areas that mattered, but still retaining the almost fully enveloped feature. The problem is that it’s so exhausting that he loses almost all of his fighting capabilities after a short period of time.
Rayleigh said that he will need to find a more energy-efficient fighting style since this is so exhausting in his body. Luffy’s gut response was “let’s make it more exhausting” essentially, lol. Which is a very Luffy style response.
Honestly all of Luffy’s Gears have been physically trying, and each one is worse for his body and stamina than the last. Gear Second is said to be bad for his health and pre timeskip he couldn’t keep it up constantly, but in battle it’s pretty fine by now. Gear Third pre timeskip was incredibly bad for him, as after just a few attacks he shrunk to an non-combat-possible size. But he has since fixed the issue. Gear Fourth of course has the stamina issue, but like his others Gears as he comes to master it I feel it will become rather easy for him to handle. Then this will bring even MORE exhausting Gears. I strongly doubt that his next level up will be a less taxing ability, that’s just not really his style.
So what would it be?
A lot of people think it will be devil fruit awakening related, I’ve seen stuff like bounce house and vulcanization. But Gear Fourth Bounce Man was in my opinion a purely Haki based upgrade of the previous gears. While Gear Fifth could completely plausibly be fruit-based, I think it’s more likely that Haki will be the main feature as that seems to be the focused power in the New World.
Full Body Armament Haki + Gear 3 or 4 size growth but compressed into the size of base-Luffy
By using Haki we have seen Luffy manipulate his body to a much greater extent in Gear Fourth. He changed Gear Third from bone to muscle balloon and then coated his relevant parts in haki to control their movement.
This is very similar to Gear Fourth but much more mastered and Haki-exhausting. Luffy will first blow up his muscles or bones to Gear 3/4 size but then by using Full Body Armament Haki he will compress his body down to a small size. He would have full manipulation instantaneously over the size and shape of his body and retain all of the power Gear Fourth has while not releasing steam or bouncing.
I think a form like this would be super badass.
*Theory by rega619