If this is the case, people would take out loans on their house and instead paying tax, they would pay interest to the bank. Yes, they could buy shares, and their capital becomes productive, but it wouldn't help the state directly rather the banks.
Official response from Gareth Morgan
No there are two ways you could apply the tax - tax the whole value of the asset and make interest deductible, or tax the equity only and don’t. The second is simpler.
Do you like this suggestion?