Please consider making the Login, Register, Lost Password and Profile pages template driven. In other words, admin pages that can be public facing.
It is very important in order to maintain a professional appearance that a user is not redirected to a completely different and unfamiliar interface whilst performing these functions. And it is also very important that this can be done without the use of a Plugin.
Something along the lines of the following would be good:
If any individual template is not present then default to the current respectively: