The commissioner may by rule define and delimit lines and classes of insurance for any purposes within the commissioner’s regulatory power, including:
(1) To delimit the underwriting powers of insurers doing business in this state;
(2) To provide a basis for determining the financial needs of insurers under s. 611.19 or comparable provisions of other chapters;
(3) To provide instructions for reports and replies under s. 601.42;
(4) To restrict combinations of lines or classes of insurance; and (5) To determine which rules under ch. 632 are applicable.