Mandatory bug-bounties from major vendors

Yeah, good luck with that (and I’m on the bounty payment committee at my company).

Leaving aside the merits of the idea, I think Apple, Google, and Microsoft would fight tooth and nail (using lots of money and lobbyists) to keep this from getting passed in the US. Even if it was passed here, it would have to be passed as a law everywhere to work. It isn’t going to happen.