Provide custom implementation of apply_completion

Is there an idiomatic way of overriding the behaviour of apply_completion in Buffer?

I see that the default semantics, which is suitable for most applications, is:

self.delete_before_cursor(-completion.start_position)
self.insert_text(completion.text)

However, I have a kind of niche use-case which would be catered for better if there was an idiomatic way to reliably change this behaviour. For example, the most general interface I can imagine is effectively a function that rewrites the line and cursor position arbitrarily.

I apologise if there's a simple Python trick that I'm unaware of that would permit me to override this (I've tried various modifications to the example autocomplete-with-control-space.py to no avail) or if permitting this could have unintended interactions with other parts of the completer infrastructure that I haven't considered.

Start by reading Buffer.apply_completion and the autocomplete-with-control-space.py example to understand how completion application is currently reached. Define what an idiomatic customization point should guarantee for arbitrary line and cursor rewrites, including its interaction with the completer infrastructure; the issue is done when that behavior is supported and documented.