I think the 15% foreign buyer tax should stay and even expand to the entire province.  
Than we can talk about how to tax those who had millions of dollars of tax-free windfall.   
1. Eliminate home owners grant for Detached homes.
2. 2% property tax surcharge on empty homes (detached homes), but exempt condos.   
3. Eliminate Capital Gains tax exemption on properties that are above 1.5 millions.   

Above measures will immediately increase supply of the right kind of homes, while keeping condo market strong, encouraging more density.