Senator Mendoza wanted to expand the Board of Supervisors in California counties with a population over 3 million to 7 members (SCA-8 ), but maybe we can refine the idea to offer more representation and more diverse political opinions. Six districts and 1 district would be given to a minority political party where the minority parties would nominate their candidates for election.
For example, in Los Angeles County, the Greens, Libertarians and Republicans would nominate their candidate for vote by the voters. Most likely the Republican would win the choice giving a 5-2 margin. Yes, our local elections are non-partisan, but to most political activists all elections have a partisan edge to them.
Orange County is usually 4-1 in composition, but Republicans are 5-0 on the board, but with the extra seat it will likely be the inverse in that county where the Democrats would win the 6th district and the minority party seat.
I would lower the threshold back to 2 million where Orange, Riverside, San Bernardino and San Diego Counties would be considered for this regulation.
Cities such as Philadelphia and Washington DC do give seats to minority parties and it would be an idea worth considering.