I did think of this before.
BB arsenal basically is alternative Immense haki
Gura Gura - alternate to AdCoC/AdCoA
Yami Yami - Alternate to Immense haki application like (Kaido , Bigmam and Law , Negating DF)
Only thing he lacks is - CoO and AdCoO
I had Viola fruit as a very good alternative to that or maybe some mythical which have a very good CoO hax , like Marco fruit has a application of logia intangiblity.
Law fruit can bypass haki.
Viola fruit with awakening might be the best alternative to CoO. but again I don't think so oda will go as far as to make viola relevent in the series again.