You may be interested in my answer (under my previous name) to this question:

• After the close ties between Britain and the Netherlands after the Great Revolution (and the diplomatic marriage), why was a Dutch King not considered in the 1708 interregnum crisis?

The answer explains why the Dutch did not have and did not want a king.

For more background on William III's role in the Dutch Republic, see my answer to the following question:

• How much influence did the prince of Orange, William III, later King of England, really had during the First Stadtholderless Period(1650-1672) in the United Provinces?