I'm glad someone else is holding him to that number too.
We should get 2 more crew members to cap off the crew. Jinbe would be good for one of them. IMO one more girl would work. Maybe make her inhuman since everyone Chopper onward has been subhuman (besides Robin).
Carrot would've been good...but I don't think she'll join. Giving her more of a back-story would feel a little crammed in at this point and every crew member had some sort of personal arc that tied in with the bigger conflict at hand before joining. She fits in with Pedro and Kin'emon as big, separate supporters for the crew.
I wouldn't mind a swordswoman from Wano joining. That could touch on the 3 Musketeers thing that was teased with Zoro, Brooke, and Kin'emon.
Speaking of, I think it'd be cool if we got some more focus on Zoro next arc like we did with Sanji for Whole Cake arc.