Theory The hidden advanced haki technique of the gorosei

There's one haki ability that I think Oda has been subtly introducing, but is yet to properly establish as haki. That is, the ability to use CoA to boost one's physical strength.

We can first see this with Lao G, whose battle insurance fist technique seems to be haki related, as evident by the black lightning coming from his body. Is this alone evidence of a haki ability?

No, but I think when you look at the composite evidence, this becomes extremely evident.

Here we see it stated that G4, a haki based technique, uses a lot of energy. We further see that

Here, it is shown how losing large amounts of CoA causes Zoro's arm to lose strength and shrivel up. Luffy's body doesn't do this, likely due to his rubber powers, but it is shown that when Luffy overuses haki, he too not only loses energy, but loses strength as well.

Look at that panel of Luffy's arm bending in on itself because Luffy no longer has the strength to hold himself up after using G4.

Basically, what we have seen through Luffy and Zoro is that CoA is deeply connected to one's strength. From Lao G, it seems that one can store CoA in order to boost up their strength.

Now this brings us to the Gorosei

A lot of people wonder how can the gorosei be a threat when they are old? Well here's the thing, the gorosei seem to have been alive for an insanely long period of time, likely due to some form of immortality(Ope Ope no mi, DFs, science, etc.). Hence they have likely had decades, if not centuries, to store up their CoA which, no doubt, is much stronger than Lao G's.

All of this means that when these guys finally do release their CoA and enter their fighting modes, its likely that very very few fighters will be capable of stopping them. This is why they, and not the admirals, will be the final enemies for the SHs(alongside Imu of course).
This is a cool idea but I think the power of the Gorosei will have more to do with the Voice of All things, as the power of the ancient weapons has to do with Voice of All things and Gorosei are also named after the planets. I’m not sure they will even be fighters so much as specialize in Voice to control certain aspects of the world the way Shirahoshi can control the sea kings