My experience with actually trying this is that current LLMs benefit greatly from having a framework to build on.

More code in the context window doesn't just increase the cost, it also degrades the overall performance of the LLM. It will start making more mistakes, cause more bugs, add more unnecessary abstractions, and write less efficient code overall.

You'll end up having to spend a significant amount of time guiding the AI to write a good framework to build on top of, and at that point you would have been better off picking an existing framework that was included in the training set.

Maybe future LLMs will do better here, but I wouldn't recommend doing this for anything larger than a landing page with current models.