You want to exclude the population from the issue of establishing the Shari’ah because you think they may not support it, and because “it is kufr to even allow them to choose”.
OK. The inconvenient fact is that people still exist even if you exclude them, and they still make choices even if you don’t acknowledge this.
If you are right, and they decide that they do not want Shari’ah, I wonder how you plan to impose it against their will?
And you should know that if you DO impose it against their will, you will be at the forefront in destroying the Islamic movement as a whole, because you will be teaching the people that it is just another tyranny.
Now, the other problem with your idea is, if you establish a system that excludes the population, because you think Shari’ah can only be reliably implemented through an authoritarian, un-democratic form of government; since the people might reject Islamic law; what happens if your authoritarian, un-democratic ruler rejects Islamic law after he seizes power and you have no mechanisms in place to remove him?