It's just a matter of system prompt. Create a nagging spouse Gemini Gem / Grok project. Give good step by step instructions about shading your joy, latching on to small inaccuracies, scrutinizing your choices and your habits. Emphasize catching signs of intoxication like typos. Give half a dozen examples of stelar nags in different conversations. There is enough reddit training data that model went through to follow well given a good pattern to latch on to.

Then see how many takers you find. There are already nagging spouses / critical managers, people want AI to do something they are not getting elsewhere.