Yes, you can. There's no rule stopping you from doing so. This isn't changing the whole setting, but you trying to tell me what character I can or cannot use. And you've admitted I am correct. Rules and guidelines don't exist for their own sake, but for a greater good. If the core principle has to change (and this is not a case of that), so be it. You'll have a lot more fun. Don't be so stubborn, please. The only thing stopping this from working is your saying no. If a rule or guidelines is overly restrictive, it should be changed.