The persons responsible for map styles should create a new one that is identical to the standard OGF/OSM style save for the possibility of custom highway and public transport signs.
JOSM allows the invention and addition of custom tags.
Custom tag styles (such as "white border, green background, white text" for Medwedian motorways) therefore are possible if the tag data is uploaded as part of the map style.
As a bonus, this would allow for visualization of situations in which for example a primary road takes upon the role of a motorway or dual carriageway for several kilometers without changing designation. This would be crucial for Medwedia, where there is a "Hurtigvej" category for expressways that are grade-separated but less important or narrower than full "Motorvej", and where the Federal Roads ("Toppelvej") often become grade-separated trunk roads.
The same applies to public transport. I want every station of the Medwed Metro/Subway to bear the respective logo (big white M on a circular blue background) on the map. Supra-terranean rail would have a big white S on a circular light green background and so on.
Could this be done?