Indeed. I have Shokz OpenRun Pro headphones, however I didn't like the sound and low loudness. Now I am using Shokz OpenFit 2 and I am happy with them. I can hear also the traffic because they are over-ear, not in-ear. The only "problem" is that L and R are not connected like in OpenRun so I have a feeling that I will loose one/them.

Oh, such an interesting rack-lock! I avoid using hanger racks if possible, also because I have rather broad handlebars and the hanger racks on the trains I use often are rather closely spaced. So I prefer to lean the bike, however with my U-lock it is almost impossible to lock it to something (which is a good idea if I don't sit close, although I haven't heard of a bike theft on the trains here in Slovenia yet).

Interesting idea! I do use the luggage block regularly (if I think well, always), however it seems a good way to attach a removable light. Good luck!