That being said, I do think standardising some form of "go ahead" message is worth considering due to the prevalence of these poor road designs, particularly in the US. In the UK, officially, you're not supposed to make any form of signal. If you must, you are supposed to just stop, but that can be ambiguous, so most people flash their lights. However, that is unambiguously against the highway code. If it was possibly to explicitly state, through a light or some other kind of means, "I am yielding my priority", that could be unambiguously understood by both AI and humans alike...

That being said, these situations where you need to rely on messages are actually reasonably rare on the UK roads and usually as a result of roadworks messing something up.

It’s my view that this is a failure in road design, and leaving it up to drivers to make up their own rules is dangerous.

Understood this is the status quo, but I wish more would be done to address these types of situations because they cause stress and accidents

Making a left hand turn into my driveway at certain times of day can take forever to do safely with cars either piling up behind me or somewhat dangerously passing on the shoulder. Even worse it's at the bottom of a hill so traffic tends to speed up. Sometimes there's a break but often someone will flash their lights and let me go.