I hope he gets good speed feats.
Best scenario: he does better than Snakeman, his speed somewhat able to catch that of G5 and Kizaru, putting an end to Sanji vs King's debate in favor of Sanji.
Worst scenario: Sanji getting fodderized after all the cool beginning.
But overall Luffy will carry and deal with both Saturn and Kizaru, what Sanji has good Is his insane durability and speed, I don't think he'll do much damage to Kizaru, but he can protect himself really good and stall if he's as strong as I believe, letting Luffy doing the damage