With all of the screentime Croco had, he never showed any different fighting skills besides of throwing dirt at people and has terrible resistance, Jinbe in the other hand doesn't have that much screentime and is already pretty impressive, an hypotetycal fight between those two would be a win for Jinbe mostly(again) because his natural advantage just like Rubber>electricity, as for Sanji, since he can CoA the shit out of Croco and Croco relys way too much on his logia, I'm pretty sure that DiableJambing him would work just fine on him and probably will be taken down after some other kicks, Croco's strength is in the past just as his relevance for the series.
Its not same as Rubber > Electricity… Luffy was natural enemy to Enel and I dont think that every Fishman or anybody else knowing Fishman Karateis nautral enemy to Crocodile.
Crocodile fought in Grand Line, not New World- 99% of people he faced there were probably many times weaker than common enemy you meet every day in New World. You know that Crocodile relied mostly on his Devil Fruit in place full of weak people compared to him. He somehow was already in New World and meet people like Whitebeard that pushed him back to Grand Line. It doesnt mean that he was weak but only that his ambitions were far too big for his strength at point in time long ago. He was kind of like Luffy in that regard with difference of Luffy being acknowledged as danger and beaten to point of loosing whole crew even before he gotten to New World.
Thanks to Kuma who saved Strawhats from fate very alike to one that Moria and Corocodile gotten with getting scarred for years because they were not up to challenge of New World.
Also as for your match up of Sanji vs Crocodile - Sanji having CoA does not mean auto-win.. Especially with fact that Crocodile powere is most difficult to fight from up close as if somebodys CoA haki is not protecting you well enough after being grabbed by Crocodile(leg, arm, head, whatever) you get turned into mummy and its end of the fight for you. Sanji being CQC fighter doesnt make anything easier.
Crocodile after 2 years being back in New World should be high caliber pirate that cannot be underestimated.
I see him as somebody who might be shown to be as strong and feared as Supernovas like Kidd for example as story goes on. Also another rival for Luffy in a way.
Also if you remember about Laws words about people just waiting those last 2 years, getting ready for something- Crocodile avoided any marines for last 2 years so he very likely was up to something and should suprise us in some way when he will be back.
Its not about him being < or > than somebody else for me, he was satysfying villain for his time and Oda kept him in story for some good reason- I would like him being enemy to some of Supernovas, Marine hellbent on capturing him(for example Dobberman going after Crocodile like Smoker goes after Luffy) etc as story goes on, like Crocodile having his adventure on his own if you get me.
Lucci also can be brought back to story, even for Kaido arc - him being in Kaido forces as a mole of some sort for somebody would be interesting. He should be able to get into crew and is very well know World Goverment agent but at same time Kaido let Drake X join who is ex marine. So Lucci being back in Kaido saga is also possible.
Oda created incredibly big world and as we can see some of secondary characters fight can be super interesting as well, especially if we will get something like that for ex-villains vs some hyped New World pirates or Supernovas.