Suppose I wanted to get rid of somebody...

How so? I drive drunk people all the time. Are you saying that “ditching them 100 miles away with no ready means to return home” has something to do with the original trip? It doesn’t. You either kidnapped them or you didn’t.

I see no where that the OP mentioned restraining the passenger by any of your definitions.

As kidnapping or restraint? I think not.

I never said it did. Sure, you may get in a heap of trouble having sex with a drunk person, but getting charged with kidnapping for driving somewhere with a drunk person who consents to going on the trip? I seriously doubt it. If you’re wasted, and I say, “Hey, Q.E.D., lets go over to Moe’s for some beer”, and you jump in my car, I don’t have to worry about kidnapping charges because you’re not sober enough to consent, regardless of whether or not I plan on providing a return trip for you.