I know an Ashkenazi man who married a Sephardi woman. When he got married, he decided that he wanted to take on her minhagim and become Sephardi. He said that he asked Rav Ovadiah zatsal, who told him that not only is he allowed to, he is supposed to, because originally the Sephardim were the majority in Eretz Yisrael, so the Ashkenazim were all supposed to become Sephardim (and Sephardim would t/f still remain the majority).
Of course, as with any second or third hand – story (second-hand for me, third-hand for you), it should be taken with a grain of salt. And I have seen piskei halacha of R’ Ovadiah’s in which he differentiated between Ashkenzaim and Sefardi which would imply that even if he said this, he may not have meant it that literally.
But I am fairly certain that at least the first part is correct (that R’ Ovadiah, zatsal, told him that he can be Sefardi).