Maybe ez, however again as an example if there are "traders" on trademe not declaring there "income" (surely not;)) then the Govt of the day via IRD needs to monitor it better and catch them. Might be cheaper than trying implement a bunch of new taxes
As I said it comes down to making a line in the sand, if you sell an asset within X timeframe your deemed a "trader" and pay tax accordingly, if there is a capital gain, i.e. income, even your own home, I knew of someone during the last property boom(before this one) moving house 3-4 times inside 2 years, , - didn't like the area after all or didn't like the house after all etc - each time banking a large profit and moving up or sideways and keeping the cash.
Anyway not sure new taxes are needed , just close/tighten some of the loopholes - as has been discussed here previously, when are you deemed a trader (buying/selling shares) , there is no hard and fast answer, these are the types of rules that need attention not a bunch of new taxes, successive governments have talked about from time to time from memory