You have a short term memory problem, don't you? We just went over this uptread. Any action to expel a state violates Article V because that act simultaneously deprives the state of representation and thus violates the Constitution.
I suspect that membership in the Senate was protected in the Constitution because the Senate was an expression of state sovereignty. As John Lansing of New York said in the ratification debates:
I believe it was undoubtedly the intention of the framers of this Constitution to make the lower house the proper, peculiar representative of the interests of the people; the Senate, of the sovereignty of the states.
Yes and whenever someone points out that Article I forbids states from entering into treaties or confederations with other states without Congressional approval you all scratch your heads and say, "Golly gee whiz, if a state secedes it isn't bound by the Constitution anymore." Well, if a state is expelled then they aren't in the Union anymore, not bound by the Constitution, and not protected by it. You all are constantly quoting the 10th Amendment saying that the right to unilaterally secede is granted to the states because it is not denied by the Constitution. Well, show me where the Constitution says the states cannot join together and expel a state if they choose to do so.