I don't see why not. The CBA should allow team owners to decide whether or not it is mandatory. You invest in a product on the ice and you should expect your assets to take every precaution to ensure their own safety.
Team owners can already make it mandatory. They can scratch/trade a player who refuses to wear a visor.
The player is the one with the MOST at stake here. They're the one who can take a life altering injury. Ultimately it should be their choice. Fans have absolutely no right to be saying things like visors should be mandatory.