Yes, but it raises barrier of entry.

Furthermore, the proposed firewall will be trivial to bypass with VPN. So that is not exactly fool-proof either.

Same issue. QC says they won't collect on CC charges to a Bitcoin trader. It becomes the Bitcoin site's problem to decide whether to sell BC to QC residents or whether to exclude them.

That still leaves all 3 gambling-addicted bitcoin miners in Quebec, but well, what can you do...

As opposed to requiring IP-based blacklists?

If a resident of Quebec is in debt, it's the province's duty to collect on it. If the province says they will not collect on debts incurred with online gambling, it becomes the gambling site's problem. It's not like the Mounties are going to come collect on credit card charges to a gambling site.