obviously not ok... .

controller.rb

def fire
  obj  = Model.new
  obj.add_blank_parts
  return obj.to_html
end

has_replacement_parts.rb

module HasReplacementParts

  def add_blank_replacement_parts
   #...
  end
 
  included do
    if method_defined? :add_blank_parts
      alias_method :old_add_blank_parts, :add_blank_parts
      define_method :add_blank_parts do
        old_add_blank_parts
        add_blank_replacement_parts
      end
    else
      alias_method :add_blank_parts, :add_blank_replacement_parts
    end
  end
end

has_returned_parts.rb

module HasReturnedParts

  def add_blank_returned_parts
   #...
  end
 
  included do
    if method_defined? :add_blank_parts
      alias_method :old_add_blank_parts, :add_blank_parts
      define_method :add_blank_parts do
        old_add_blank_parts
        add_blank_returned_parts
      end
    else
      alias_method :add_blank_parts, :add_blank_returned_parts
    end
  end
end

report.rb

class Report
  include HasReturnedParts
  include HasReplacementParts
  
end