(1) Except as otherwise provided in this part or part 13, all powers of the consolidated municipality are vested in a commission. (2) (a) In consolidated municipalities having a taxable valuation of $50 million or more, the commission must consist of seven members. (b) In consolidated municipalities having a taxable valuation of $12.5 million or more and less than $50 million, the commission must consist of five members. (c) In consolidated municipalities having a taxable valuation of less than $12.5 million, the commission must consist of three members.