first of all - I really do like the smoothing modifier. But I feel that it could use some refinements.
When youre using it for smoothing of clothing, which I guess is what most people use it for anyways, you usually only want it to work in a way that the silhouette of the item aligns with the bodypart below it.
Lets take a stocking for example. I take this one because it seems that this can cause alot of trouble depending on the pose. When you use the smoothing modifier for a stocking in default pose it usually works very well in almost all cases. But once you bend the legs so the shin and thigh intersect, you end up with ugly artifacts where the bodyparts intersect.
I dont know how the smoothing algorithm works under the hood but would it be possible for you to add a check into it that looks up to which bodypart the current polygon that will be smoothed belongs? This way you could use the bodypart groups so that only the parts that belong together will be smoothed accordingly. This would ensure that the thigh polygons of the stocking would only be aligned towards those on the thogh of the figure. You would prevent things like artifacts when an arm touches the leg while posing, which usually leaves some holes in the stocking or the smoothing even drags the stocking a bit over the fingers/hand in that case as if it would encase the hand.
Adding a checkbox or some value as to how much it should make sure to keep its base form or simply align just to the model that its derived from might really add an easy way to fix those artifacts.
I must say that those things really drive me crazy on stockings and other bits. The postwork and/or the polygon correction before rendering take alot of time so it would be great to have something that makes sure that those artifacts dont happen.
The attachment image shows all the artifacts I mentioned in this post.