[RFC] traffic signs national id and human readable values (traffic_sign=* and traffic_sign:id=*)

This would not help - others would definitely do it anyway.

To avoid stealthy deprecation proposal would need to admit that it is deprecating things or it needs to approve multiple tagging schemes at once. And yes: both will not be liked by some other mappers.

Or proposal needs to limit itself to areas where no competing established tagging exists.

If traffic_sign=restriction is not a part of a proposal then why it is on the proposal page on page listing what will be approved?

https://wiki.openstreetmap.org/wiki/Proposal:Extended_traffic_signs_tagging

screen06

by placing node at position of traffic sign, next to road it acts on? In rare cases where match to road is not obvious description can be added

No idea, not checked. Maybe these are intended to be machine-readable? You can link their documentation if you want fuller answer.

???

By using other orientation methods like already mapped objects or aerial imagery?

I do not understand this part.