Why would this be a good idea?

it would not be useful. Even a large number of programming books will not overcome the weighting of all the terrible source code and pitifully inadequate and often wrong explanations of programming topics that an LLM has.

Beyond that, all the LLM will do is recommend best practices. Sure, it's great to keep best practices in mind, but you have to realize that best practices really lags current practice, and do not even come close to excellent programming. Religiously follow "best practices" without care and you will have garbage programming. I give you the example of large numbers of website asking you to create a password with really exotic character combinations. In an HTML "password" field that shows you dots, so you're doing it blind. Twice, to make sure you typed what you thought. It's bullshit, and it's a "best practice". There's also no incentive to rid ourselves of no longer relevant, or mistaken, best practices. Something screws up when you didn't follow a mistaken best practice? You're at fault for not following a best practice, no matter how horrible.