All, thank you for ideas and list! DrYak, the following were filed:

https://github.com/rinigus/pure-maps/issues/76
https://github.com/rinigus/pure-maps/issues/77
https://github.com/rinigus/pure-maps/issues/78
https://github.com/rinigus/pure-maps/issues/79

Sign colors could be different. I saw MapQuest API had support for it, I'll have to see whether we can ask Valhalla devs to support it as well. Same probably with the speed sign (US vs EU).

Re auto scale: would be good to implement - have been thinking about it earlier.

Signaling when speed exceeds more than 5mh/h - let's see when/if we get there. Skipping for now, maybe later if all starts demanding it (see below)

Re fish-eye: would require changes in MapboxGL. Probably should file there.

Easter eggs - sure!

I am swamped for few weeks with porting Pure Maps and OSM Scout Server to Linux desktop. This is a part of an effort to bring the maps to Librem 5 (Puri.sm team got in touch with me after r0kk3rz advertisement, thank you!). So, I'll be working with the designers behind L5 and I would expect many useful recommendations from them. Maybe we can also figure out what to do with the landscape mode.

Current work is on moving Silica-dependent parts into separate folder and then have, through such separate folders, support for Sailfish, desktop, and L5. In practice, I expect that SFOS end-users will not even notice that they run cross-platform apps. Something along @MartinK universal components (same basic idea), but tailored originally only towards two applications. Let's see if I can later join that code with UC's.

In the end, I expect that this time investment (in addition to fun), will pay off by having more people using the same application and, one can hope, more developers working on different aspects of the map applications (client and offline server).

Re landscape mode: yes, I was thinking how to use left/right. That's why speed, speed limit, signs, and time/distance left are on the sides. Full street name will not fit there, though. Already now, in some places, next maneuver street names could be cut on the top. Although, its not as short as in portrait.