The Broadcasting Act 1989 is a 20 year old fossil that has barely kept up to date with changes in the current media landscape, media technology and the spread of new media. It probably needs wholesale re-writing but a priority could be to repeal the discriminatory Section 81 and Section 79A, which prohibit NZ television stations from broadcasting advertising and electoral programmes on Sunday mornings and listed Christian and secular holy days.
The discrimination lies in the fact that other forms of media (radio, newspapers, magazines, the internet) are allowed to advertise in those timezones. There is no logical reason why television should be singled out for special (anti-competitive) treatment.
I presume a change like this would appeal to pro-market MPs too, which makes the scope for getting an MP to table it wider.