This is actually not a new idea and has been in Everything2.com for ages. Since perlmonks.org also run on the same engine, it is not difficult to implement. This sort of action is called blessing and cursing and is only available to users of some level (can't remember which one, but somewhere pretty high). Let's say a user of certain level can issue one blessing or cursing every day to any other user. A blessing and cursing translates directly into XP change in everything2.com AFAIK.
I think it is a nice idea, especially if these powers are given at a certain point, let's say after reaching pontiff or bishop level. People who reach this sort of level are less likely to use it for abuse.