Ending MIQ is inevitable but it's a one-way decision. Once the virus takes hold there's no going back, even if you take quarantine and isolation to China levels. Nobody likes a lockdown. My opinion is that the right time is when the globally dominant variant is a fast-spreading one with a proven hospitalisation rate post-wave that is lower than what NZ could cope with, given the vaccination rate. Omicron could be a candidate but its wave is still spreading, so it's too early to tell.
As for MIQ dues, the government and therefore the people bear its cost. NZ$13 million isn't a trivial sum, but it isn't huge either, so while any scheme to reduce the burden would be welcome, a plan with a huge potential cost such as ending MIQ is a bit too much risk, especially with Omicron data coming soon on the horizon.