It's a tough road.

Your idea is novel in itself, but not unique in RPing. I'm currently running a (very slow) murder mystery. It's no secret that the player characters are among the targets, and nobody has died yet. I've also seen games based on the Werewolves/Mafia parlour game (in which players have to vote to kill off a secret traitor, who is working against them).

Honestly, if you clearly explain that characters are going to die and that other players will have a hand in it, and somebody throws a tantrum because they got murdered, show them the door. Healthy player competition is what will force players to ally themselves with one another and play tactically - technically, this is metagaming, but some people (like me) don't have problems with it in some games (like this one).

The problem you're going to have is balancing keeping true to the Anybody Can Die principle and not scaring people off. I would definitely think twice about making a decent character and commit to an RP whose second page I might not even get to. I'm not saying it would stop me (it hasn't stopped the players in my Murder Mystery), but it might thin out your interest. If character deaths being influenced by the other players is a plot-point, you may have to think about what you do if a player drops out.

In principle, mandatory character deaths can and do work. On a side-thought, God knows I've GM'd games and killed off player characters whose players have dropped out (either spitefully or with their blessing!). The only difference here is that it's working the other way round.