The state agency shall not finally refuse to approve a plan submitted by a political subdivision under section 68-608, nor any proposed amendment to such plan, and shall not terminate an approved plan, without reasonable notice and opportunity for hearing to the political subdivision affected thereby, nor with respect to the employees of such a political subdivision who are members of a retirement system, until such political subdivision has proposed and adopted a method that is acceptable to the members concerned of protecting the retirement rights and expectancies of such members.