So muscle and booty sliders..

[Shurrikhan]

There's always someone who has to be special and difficult. ¬¬

The general consensus seems to be that people want a booty rather than an ironing board as their behind. It just seems like a much easier fix to update every models behind to a certain level, rather than wasting even more resources on creating a slider. (Assuming that does indeed require more resources.) If they're going to update the character creation, I'd much rather they go with more face options tbh.

Ad homenums aside...

1. We have a breast slider.
2. One would naturally expect breast size to correlate, roughly proportionately, with butt size.
3. At present it does not, and cannot.
4. Setting a single rear size would match a single breast size. It would retain the same issue as now above or below that size that the current rear size has for breast sizes above the minimum -- to which it is basically matched.
5. A single rear size nearer to matching the center of the breast size range, given that most players set themselves around or above the middlemost breast size, would be an improvement, but in classic SE fashion, would not solve the issue.
6. Similarly, matching butt size precisely to breast size would deny some (small) form of player expression. As such, a slider may be a small improvement over automatic scaling, but it is also an objective improvement.

As with breast size in XIV already, the range for a butt slider does not need to be ridiculous.

Alas...developers at every step seem to complain about extremely horrid engine and legacy coding that no one in their right mind would use for anything but an hour long or so indie game, let alone large MMO title...But hey, there are exceptions, right?!...

This. If referring to Crystal Tools and the 1.x netcode, Yoshida already used the replacement of 'all former netcode, except as was necessary to retain legacy character item and appearance information' (note that the effects of those hair color, skin color, and slider choices were not wholly retained despite this, as they did not align with the new palettes -- hence the free re-customization to accommodate the reduced character poly count and new engine shaders), as the reason ARR had to be as bare-bone as it was.
Congratulations on your upgrade: gear now fits upon the body as if a steel mesh were fit under every skirt, and balloons beneath the cut of every shirt.

If referring to Luminous, then that's just too sad for a even a retort.