Quoting justanothamotha:" So what if you make those changes & the kid starts being bullied for another reason? Will you make ... [snip!] ... self esteem come from finding a way to be okay with yourself regardless of whether other people are or aren't okay with you?"
That's something that comes with adulthood.
I would never send my child to school with smurfed eyebrows/weird clothes etc. to begin with. However if there was something physical she was being made fun of for (ie. big nose), no I wouldn't change that. If she wanted to change her hair colour because she was made fun of I'd let her, I wouldn't suggest that though.
Basically I would allow her to change whatever she
wants, but I would not be getting her plastic surgery or pinning her ears to the side, etc. And of course I would teach her that she should be okay with herself (etc.) but that usually falls on deaf ears to kids who are being bullied.