You state this like it's an obvious measure; you're irrational over 2 months is my rational over 2 years.
Vancouver was absolutely booming in February after some of the steam was released in late 2019. Those vacancies are primarily because owners are using the house as a value store. How would caps on initial rental rates help at all? Those same owners would just never list them.
Rather than arbirtrarily cutting owners off at the knees, forcing them out, it would seem easier if you just left the area.