A consensus is firming up on campaign funding law reform because National has signaled a willingness to support curbs on third party advertising and a clampdown on anonymous donations - see National backs curbs on funding
This incredibly shift by National indicates how much change the party is undergoing under Key/English. But it is also a sign of Key and English's incredibly flexibility and ability to read the writing on the way in this regard. They probably realise that any new rules that come about will probably not change campaign finance activity that much in the end, and so it's wise for National to proactively remove the stick that they're being beaten with - especially after the Hager book.
Furthermore, National are taken the opportunity to bring their own electoral complaints to the table. Bill English says there should be a moratorium on non-essentialy government advertising in the run up to the election. This seems a perfectly sensible idea, and it's certainly true that parties in power have strongly exploited this multi-million dollar lever of power - but not just within the 90-day election campaign period that English suggests.
National also suggests stronger penalties for parties breaching spending limits - as Labour did in 2005 and was unpunished for. Again, such a proposal is sensible if you are going to have caps on spending.
The Green Party has also indicated support for restricting third party advertising, but with the unusual idea that the spending of such organisations should count against the cap of the party they are supporting. Such a law would be very complicated, fraught, and probably still rather undemocratic.