<<Read again, I never said that a player should be declared the winner because he has more pieces, I said that he should be declared the winner because he would kill the opponent's king in the next move.>>
And I told you why such an idea is daft. The game cannot get that far. Simple as that.
The game should end when a king is killed. Imagine how satisfying would it be to see how your pieces kill the king.
Yes, that should be legal!
If you are dumb enough to not notice that you are putting your king in a threatened square you deserve to pay for it.
At some clubs they actually legalized this move when playing Blitz or bullet.