I agree with all your points regarding offshore nationals, but strongly disagree with your comment regarding taxing Canadians who own second properties even more.

30% of condominiums are in the rental pool.  Without this supply rents would be far higher.

80% of Canadians have no pension plan beyond the pitifully inadequate CPP.  My experience says most of the buyers condominiums who rent these properties are long term investors who are using the property to fund their old age.  They buy them with after tax dollars, don't get a tax deduction for retirement savings,  pay taxes on the income, and capital gains taxes on selling.