Thanks for your effort, there is definitely room for improvement.
Some ideas which are not optimal today.
We had a discussion about regularly (night, weekend) switched off traffic signals. Do you see how this could be implemented?
For a few years in Austria we have a red turn for bicycles after a stop. We map it mainly with relations which is ok but complicated. Could this be made easier?
Cycleways are somewhere in between streets and footways. If a street is crossed by a cycleway, I would map it as crossing=traffic_signals and the cycleway is expected to be “the crossing way”. If a cycleway is crossed by a footway, this is not the case. Then, the footway is “the crossing way”. Because this is not clear, subtags like button_operated are ambiguous.