Sanji isn't facing Gorosei.
Sanji having an opponent among group that Zoro faces is always iffy.
He didn't get to beat Doffy executive
Didn't get to 1v1 Enel's Priests
Didn't face a Yonko
Had no opponent in Punk Hazard
Shared his opponent with Jinbei in FMI
Sanji's final battle is kizaru.
Oda respects AdvCoC too much, look at how Kizaru got stomped.
Zoro vs Kizaru and same thing happens.
And I don't think Oda will give Gorosei largest CoC in the series and have Sanji beat them. He is unfortunately not that important.