Except for a proposal for the merger of a then existing subsidiary district, any proposal for a merger or establishment of a subsidiary district authorized by this division shall contain a request in the alternative, requesting either a merger or the establishment of a subsidiary district, as may be determined during the course of the proceedings. Any proposal requesting only merger shall be deemed to also include a request for the establishment of a subsidiary district and any proposal requesting only the establishment of a subsidiary district shall be deemed to also include a request for merger.