Why do you think “separation of powers is a Jewish concept?”
If I’m not mistaken, our kings had all 3 powers.
The Chashmona’im were punished for taking the throne despite not being
of the royal family. You’ll have to find another source to support that idea.
Can there be an executive without a state?
(What did you mean by “legislative powers are from Sinai”
and by “involved laypersons?”)