wouldn't really like it in one piece, it wouldn't fit that well with their characters tbh. Robin and Nami may be "showy" but their personalities don't align with the broads in ecchi anime
The ecchi in Fairy Tail doesn't ruin it. what ruins it is that it is not much else except BS "believe" power ups and little actual work.
OT: Doesn't need it. has enough perverseness in it for me, I mean look at nami and robin pre TS vs post. Also Franky. If they add ecchi it takes away time from actual plot which is the strongest point about one piece. It has good plot.