Proposal background: The Auckland merged city structure should be governed by city-wide visions and policies. The new Auckland Councillors will, after all, represent the total population of the isthmus, not parochial interests. The way they are elected should reflect this, and electors should be given the chance to vote on policies for the city rather than be distracted by personality politics and contests.
Electoral system for Auckland City: The city should be established as one constituency, not split up into wards. All Auckland electors can vote to elect Councillors from one ballot listing all tickets and candidates.
20 Councillors (but preferably more, say, 50) should be elected from ticket/party lists applying strict proportionality in the voting system: 5% of the valid vote yields one seat. In the case of 50 seats the threshold falls to 2%.
Voters choose one candidate on the ballot (organised in ticket lists of maximum 20 candidates - independents can stand too and be subject to the same threshold).
When votes are counted the total of all candidates on each individual list will be tallied to determine how many seats the list is awarded on the Council: 1 seat per 5%.
All individual candidates who clear the threshold hurdle will be automatically elected. If more than one seat is won by the list, they go to the highest polling candidates on that list.
Note that this does not mean your placement on the list will trump votes received by another candidate on your list - list leaders will thus not automatically be elected when the list clears the threshold.
Independent candidates outside the lists will need to clear the threshold in their own vote to be elected. The "leftover" effect of the lists means that independents are actually encouraged to organise themselves into lists in order to profit from the same effect. This will benefit voters as lists will emphasise policy and vision instead of glamour or single issues.
The system is easy to understand and administer, does not distort vote weight (all votes are equally valid) and lists will have space for a wider variety of candidates than under any other system based on ward representation.
There is also no need for separate reserved seats for Maori or any other group because a low threshold will ensure a possible wide variety and proportionality of representation.
There is even no need for a separate election for mayor. Like in the parliamentary system, the largest faction elected on the Council should have first dibs on forming an Auckland government with its leader as Mayor. This will greatly help integrating the mayoral office with the power structure on the Council.