Well... there are some basic issues here. First of all any time you decide to increase growth of tissues where there would otherwise be none, you run the risk o

Well... there are some basic issues here. First of all any time you decide to increase growth of tissues where there would otherwise be none, you run the risk of cancer. I'm not sure how (other than breaking and resetting bone) you'd get people taller, and what the other issues would be. You'd also need to make sure the quality of bone is still high, that the growth doesn't lead to fractures or issues with the connective tissues. You're essentially trying to reboot a major organ system which both supports your entire body and contains the machinery for making blood and immune cells. That's a huge risk for an incredibly modest reward. Meanwhile bleaching people is a dangerous, unwise, but still quite straightforward thing to do. You don't have to reprogram anything fundamental, you just use a cocktail of nastiness which has the desired effect at a very superficial level.