I really don't suggest it, even if it looks ok to start, eventually it will not look good. The ink will fade, or your brows will change color with age and then there will be a marked contrast, or worse if you skin starts sagging, there will be inked areas in inconvenient places.
I don't have issues with tattoos in general, but the idea of make-up tattooing just seems like a bit too much.
pro, your friends might like it... con, it will make it really hard for you to get a job and be taken seriously for the work you do (But i'm just making an assumption).
Now, if you have thought this through and thought about how it could affect you in the future and think it's all cool, go for it. But It's up to you. I personally wouldn't because I plan to be a biotechnologist, but it's your decision.