Section 6. The amount of group life insurance on each employee shall be five thousand dollars, and the amount of group accidental death and dismemberment insurance on each employee shall be five thousand dollars, except that those employees desiring to elect optional coverage in excess of five thousand dollars group life insurance and five thousand dollars group accidental death and dismemberment insurance may do so as provided in section ten A. The amount of the hospital, surgical, medical, dental and other health insurance benefits to be provided each employee and his dependents shall be determined by the commission as provided under sections four and ten C. For active and retired employees, their dependents and the survivors of deceased employees, including municipal subscribers, except as otherwise required by state or federal law, and except effective July 1 of any year, the commission shall not alter the schedule of copayments and deductibles for health plans, or alter any other terms relating to health plans which would require authorization by vote of the commissioners but, for health plans whose rates change on January 1 instead of July 1, the commission may make such changes effective January 1. If the governor reduces allotments to the commission under section 9C of chapter 29, the commission may make any necessary adjustments to account for the reduction, but the commission shall not alter the contribution ratios provided in the most recent applicable appropriation act. As determined by the rules and regulations of the commission, all insurance coverages authorized by this chapter may be considered separable for employee, retiree or deferred retiree application and eligibility purposes.