When I player asks to play something at the margins or outside of those parameters, i think it can be useful to re-examine the parameters as GM and ask if they are really necessary.It is my policy to start out with the assumption a player is making a good faith effort to create a character within the parameters set forth by the campaign. Those assumptions have tested my faith at times. As a GM, I try to make a good faith effort of my own to accommodate players though it isn't always possible. Each case needs to be examined individually.