A New Zealand MMP election does two things:
- It decides which parties will be eligible to be allocated seats in parliament.
- It allocates those seats in parliament in proportion to (eligible) voter support.
Only people who voted for a winning party in step 1 may take part in step 2.
I think that every voter should have a say at step 2.
Two choice party voting does that, without the need to change the threshold percentage or any other aspect of the MMP system.