Tattoos can only be removed via laser treatment currently.

what are the pros and cons of tattoo removal other than it is expensive and painful, but can you use it to lighten up a tattoo enough to get another one on top if a good enough cover up can not be done?
yep. You can. Infact a lot of people do this. Even with a lot of laser treatments, sometimes the tattoo will still be there, albeit pretty faded. So they'll get a cover up. By the way, you can use white to lighten up a tattoo, but it likely won't work as well as you think it's going to.

Tattoos can only be removed via laser treatment currently. Unfortunately, it is a rather painful procedure, as you're essentially burning off the top layer of your skin, where the tattoo pigments are. And more often than not, there'll be a bit of scaring, as well as some remnants of dye left. So yes, many people do cover up with another tatt design after a while.You can try and lighten the scarring with creams designed to do so...you can consult a dermatologist for this. As for the dye remnants, I'm afraid they stay.