@MarchHare
Well, IMO there is a lil difference in strength between fishmen.
Oda gave us slight hints. When the NFP-officers left to the plaza, citizens were afraid of the officers and sayin stuff like:
"The NFP are dangerous. I heard there are 4 types of sharks and a giant squid among them."
To me it seems Oda wants to show us that shark-fishmen as well as "the more dangerous fish"-fishmen are stronger than "normal" fishmen.
If we look @ Arlongs crew we got only one shark-fishman: a sawshark-fishman as their boss being the strongest of them.
And Oda was keeping shark-fishmen up his sleeve until this very arc. Hody being a great white shark makes me believe that in pure strength Hody is stronger than Arlong though "lackin of experience". At least a great white shark sounds more dangerous than a sawshark to me.
IMO it seems like Oda just want to say to us:"Those NFP-officers are among the strongest fishmen in the current timeline, they're sharks after all!"
Tiger is the big exception: his type of fish sounds rather harmless.
Well, thats my opinion. Its easy to understand and not everything in OP has to be super-complicated. Sumtimes its as simple as it seems.
Bout the ES:
We don't know anything bout BigMom yet.
We know that she has like curled hair, fatass lips, maybe an affinity to trees/nature and likes candy. I'm glad u 2 think that Lola is BigMom's daughter (it is obvious anyway).
I c the problem with the Yonkou: if Shanks and Bigmom are on Luffy's side, it'd mean that Kaidou is the only "bad yonkou" left, but we still got BB left and also the "new shichibukai" and the SNs. I don't c big clashes with each SN, but the SHs will ran into one of 'em from time to time. There is also the marine and the WG as an enemy. It could also turn out that BigMom is a BigBitch like u say, but yet we've got no idea how she is like.
I'd like it if Dofla was the provider of the ES. It would skyrocket his badassness and his role as an antaghonist. But the fact that he isn't interested in slavery anymore makes me doubt he has anything to do with the NFP. If its Dofla it has nothin to do with the slavery of fishmen, but that chaos new age he was talkin about.