Section 54. Modification of alternative form after adoption

A county which
  shall have adopted an alternative form of county government may, in like
  manner and with like approval of the electors of the county, as provided
  by this chapter for submission and adoption of an  alternative  form  of
  county   government,  supplement  the  form  of  government  theretofore
  approved by adding thereto any provisions which might have been  adopted
  originally or delete or change any provisions of the form so as to leave
  it  in a modified form which could have been adopted originally, and the
  form of government as thus modified shall, from and after  the  time  it
  becomes effective, have the force and effect of, and be deemed to be, an
  alternative form of county government.