While proceedings are pending under any petition or resolution relating to reclassification of a municipality or reorganization of the government thereof pursuant to this chapter, no resolution shall be passed for the purpose of initiating other such proceedings or submitting other such proposals to the voters at an election thereunder; and no petition for reclassification or reorganization of such municipality shall be accepted for filing pending such proceedings, except that a timely and sufficient petition seeking to place on the ballot for such election a proposal for an alternative plan of government authorized by this title, as provided in RCW 35A.02.090, may be filed and acted upon.