Originally Posted by
LordMcMutton
Rather than a side effect, that's generally the very reason to use the method- it's why it makes it easier, due to removing the need to recreate the UVs and rigging on each one.
On whether or not they can implement sliders, it's possible for an older engine like theirs not to have the function to interact with shape keys. Looking at what we have now in terms of sliders:
The Height and Tail sliders scale the armature, and the Musculature slider overlays a normal map, which leaves the Bust slider as the only possibility for knowing if it's implemented already- I can see that being either bones again, or shapekeys.