I read what I put, and then I read what you put, and I really don't know what you are asking me.

Your post implied that secular political power for certain religious groups within a country was allocated upon the number of people who were members of a specific religion (ie confession). Thus, if people convert away, then the religion will lose the number of seats in the legislature, or jobs, or tax dollars, etc that they get.
I can't think of any country that counts the number of adherants of a religion when giving specific religious groups direct political power AND permits people to change religions. Such as the Archbishop of Canterbury sits in the House of Lords by virtue of being Archbishop of Canterbury.