I think the worst-case scenario would be being pregnant at the time of vampirization.
As far as hair goes, SM has said that hair remains human since it is composed of dead cells and thus does not get transformed. I would imagine that the hair follicles get vampirized, so that hair is attached very firmly to the skin, but it can definitely be cut or shaved off. I would also imagine that if hair is cut or shaved after the change that it is done very, very carefully, as there is no re-growth.
Other things like skin issues (acne, blemishes, scars, etc.) get fixed during the transformation process as flesh is repaired and restored. The process as described by SM suggests that the venom absorbs the human DNA and first perfects it, then vampirizes or crystallizes it. Witness Emmett’s attack by the grizzly; there would have been at least some gouging of the flesh by the bear, which was restored and repaired by the venom.
Unknown is whether amputated bone or lost tooth enamel is actually restored. Tooth whitening (and at least some straightening) would be par for the course.
I think it would (suck) to have harry armpits. But what if you had breast implants? Would the implants go away and leave the girls saggy?
That is actually a very good point. Here is my theory: the breast implants would remain as they are not considered flesh, sinew, or bone, and the venom would ignore them. How about an alternative issue? Suppose there were screws in your bones that were used to repair your knee? That wouldn’t be like a breast implant that the venom could work around. The screws (I think) would be more like an injury to the bone that the venom would try to repair. I have no idea what would happen in that case. A fairly easy solution would be to state that the venom dissolves any foreign object in the body (thus taking care of the breast implants issue) at the time of the change, but then SM has never elaborated on that problem.
Also, as far as general physique is concerned, I think there would be some reduction of general body fat, along with an increase in muscle mass and tone, but there are definitely limits. SM has stated that Esme’s physique was slightly rounder than the others because she had just given birth a few days before.