If sanji never know the truth

[Star_Of_Hope]

I believe he would be happy marrying pudding. If only big mom stays true to get word, then may be sanji would love as a prince from here on in.
Except for his brothers and Dad, I don't see any other disadvantage with this outcome

 

[Kaname]

That is a possibility. If you are caught with the latest anime episodes then you would know that Sanji is excited about the marriage with pudding