The ethical dilemma arises if you lose the wager, and despite your bravado, you do not know whether or not you would win it. That’s why it’s an ethical dilemma.
I think it is naive to think we would process this individual the way we process defectively-behaving (regular) humans. Not a chance. We have a process in place to deal with lawbreakers and assholes; another process in place for people we think are mentally defective and can’t help their behavior. The first we imprison; the second we institutionalize. Neither tend to be especially content. Both are products of reproductive couplings we cannot control. Within our own populations, we do not typically control who gets to procreate, and whether or not they should be procreating. (Octomom, anyone?) If Neandertal behaves badly, we cage him up, and there is no such thing as due process. He cannot be held to a standard of law.
Creation of a Neandertal is qualitatively different from procreating ourselves. We know in advance that we are not creating our own population–our own subspecies going back 200K years. Therefore, if such a being ends up being wretched, it’s not some accidental variation secondary to ungovernable procreative urges. It’s a being whose misfit-ness might be exactly due to his fundamental nature. If that misfit-ness does occur, we who created him knowing that his gene pool was substantially variant, and at the same time knowing it was close enough to ours to make him seem like one of us, are responsible for him. We are his Masters. We are his Creator in a much different sense of just being his biological parents. And therefore we are responsible for any misery that arises, and responsible to make a decision whether or not to euthanize him he turns out to be miserable. Since I wouldn’t euthanize an individual so close to my own kind, I don’t want to create him in the first place.
If John Mace creates him, I’d hold John Mace personally responsible for the Neandertal’s personal contented-ness and behaviour in a much different way than I’d hold John Mace personally responsible for having a kid who is a jerk or who is unhappy.