> no developer should be proposing branches over 1k loc

I've seen that reaction many times. It seems to work well enough when someone is maintaining existing code. However, greenfield projects can often require literally orders of magnitude more code to deliver something that can be integration tested.

The first step is to break it up into a stack of commits. Each one must compile and pass its unit tests, of course. Keeping it under 1k loc of released executable code is usually easy, but often becomes difficult to impossible if you want well commented code with excellent unit test coverage.

Assuming you have kept all your commits under 1k loc, there is still the problem of whether you present them in one PR, or as a stack of PRs. The issue with a stack is why an API is designed a certain way often isn't evident until you see how it's used. Responses to PR comments are explanations that point to later PRs in the stack, which is irritating for both the reviewer and the author.

I haven't found a good solution. I'm not sure there is one.