Subject to the approval of the Commissioner under such procedures as he may develop, health care insurers may place reasonable limits on the number or classes of preferred providers which satisfy the standards set forth by the health care insurer, provided that there be no discrimination against providers on the basis of religion, race, color, national origin, age, sex, or marital or corporate status, and provided, further, that all health care providers within any defined service area who are licensed and qualified to render the services covered by the preferred provider arrangement and who satisfy the standards set forth by the health care insurer shall be given the opportunity to apply and to become a preferred provider.