The three things you mention are exactly the problems that will occur if the flaw is not fixed - as I said you have got things the wrong way round.
I am already witnessing people not trying to stop another from winning, and a likely win that I haven't been able to do much about due to unlucky placement, and that's just in one single game! As for people dropping out, no system will prevent people reduced to very weak position from giving up, proper WTA does not encourage it any more than flawed WTA or PPS. But in a variant where grand alliances are encouraged, there are better opportunities for recovery.
If you increase the relative value of a win, people are more likely to try to win. I really don't see how you can argue the opposite. As for luck, that's subjective, one man's luck is another man's cunning manipulation and maximising opportunities. If you can persuade someone to lay down their life to help you win, does that make you the best Diplomat ever, or someone who is just lucky to have a fool to hand when he needs one? However in a game where everyone is independent and every alliance is agreed only because both parties believe it is necessary to help them achieve the win, how can you argue that luck will decide such a game?