Its strange, but I was just thinking about this. I think that a Canadian State Crown would be a marvelous symbol of Royal Authority. The Sovereign would obviously be the only person to wear it, during our State Opening of Parliament it could be displayed before the Governor-General so to symbolize the authority of the Sovereign. I hear they do the same thing for the Opening of the Scottish Parliament.
While I don't see this Crown being made in the near-future. Where would it be kept? We don't exactly have a spare Tower of London lying around Ottawa, maybe at Rideau Hall, it is the Official Residence of the Sovereign. Or at Le Citadelle in Quebec City. It is a Fortress after all and a Residence of the Governor General.