I go by this. Even Repliku's death wasn't really a proper death but more subtle with him fading away while acknowledging the fakeness and falseness of his existence and life.
I don't know, it kind of seems like Riku himself doesn't think the Replica is so much different - he says, pretty confidently, that the Replica's heart will go somewhere, and probably the same place his will.
Plus, some of the Disney villains die. Clayton dies - he gets killed by his Heartless helper falling on him. Shan Yu dies - he's clearly still human when Mulan and Sora's group take him down.
Ansem died too, though that was off-screen so I don't know if that counts. It's just the good guys who have such a high survival rate, though.
I am curious as to what happened to Ven in light of him wanting to be Erased and Roxas though, so if anyone might get that close to a physical death, my bet is riding on him with him presenting Kingdom Hearts' version of a suicide.
Again, there is no difference between "erase me" and "kill me." The Japanese verb used (kesu) is the same that Riku uses when he asked Mickey to destroy him if Ansem wins, and the intent was clear there. From what I read, it's a euphemism that got translated literally because most of the English equivalents sound terrible in that context.
As for the suicide thing, KH characters in general tend to have rather suicidal tendencies, but it's always for some purpose, and I imagine it's the same thing here. I'd imagine it'd be something pretty similar to Riku's request, actually.