Edsel, I'll cut to the chase. In at least 2 posts you've indicated a potential action of "creating a payroll in December," and in your latest post you made the decision by "weighing upsides and downsides."
If by "creating" you mean to backdate a check to December to make that payroll, that would be illegal and unethical. Don't do it. I would view this action as fraudulent and unethical; a sham no different than manipulations to maximize the earned income credit. We can correct errors in classifying existing transactions that actually occurred during the year, but we shouldn't be creating transactions after the fact to arrive at a more favorable result.
If by "weighing" you mean to consider an action based on the benefit to the client over the legality or ethical practices as a preparer. First and foremost, your decision should be based on law and ethics, and only when what you are considering falls within that scope should the benefit to the client be considered.