Like many people faced with getting a visa, you would like to read your future. Sympathies, and I'm not being flippant, but there isn't a sure-fire way to do this.
So, some thoughts on your questions - but these are just the thoughts of a lay person, without any force of certainty, and will still leave you with your own concerns and decisions.
The Christchurch rebuild is a HUGE project. Of course there's no way to tell exactly how long it's going to take, but so far, there hasn't been any sign of the special arrangements for foreign workers being wound down - the whole routine work of INZ in New Zealand has been altered to accommodate the extra work involved in processing visas for the skilled immigrants needed.
Labour market check. Yes, if one particular employer can show s/he's drawn a blank in finding a suitable NZ national or visa holder to fill his vacancy, having run a reasonable amount of advertising, he can get approval. This is entirely based on the THE ONE case, so nobody is going to be stopping him hiring his foreign applicant on the grounds that there are e.g. painters at the north of North Island looking for work, when he's at the south of South Island. But INZ are aware of all the wrinkles. Here are the instructions on this point.
http://www.immigration.govt.nz/opsmanual/45981.htm
It still seems likely that the largest need for
extra painters is going to be around Christchurch. There aren't huge building projects elsewhere in the country, and it's the kind of skill where, in normal circumstances, each area tends to 'grow' and support the appropriate number of small businesses.
http://www.awpa.gov.au/our-work/labo...cupations.aspx applies to Australia - the immigration requirements of the two countries are entirely separate. Don't be fooled by the fact that they share job definitions in the form of the ANZSCO list. Painter is on the CSSL and the List of Skilled Occupations, and it can't be denied as the latter. (In quite recent years, for instance, the teaching profession got removed from the LTSSL when it came to the point that NZ had trained enough nationals to cover the serious lack there had been, but the job still remains as a Skilled Occupation, so if someone gets a job offer, it can lead to Residence.)