I think I've figured out the reason we won't get butt sliders and it has to do with the same reason why any sliders don't work with ffxiv's glams. FFXIV glamour isn't real, a lot of it is one clothe with locked proportions. If they added more sliders none of it would change on the clothes themselves because every race has different proportions so they lock it.

Wonder why they haven't unlocked race starting clothes for other races? it's this very reason, the only clothes that take character sliders into consideration is anything made for that race.So next time when Yoshida says it's because the clothes would stretch weird just tell him that's not true. It's because they don't want to list every cloth piece per race (so that sliders take effect). My hope is that if we speak about it now we'll fix this glamour problem by 5.0. No sliders will ever work unless they do this change.