Hi Marko,
FWIW, I just defined a 25km route relation that could be useful for testing: http://www.openstreetmap.org/browse/relation/3252216 IMO, this is much better than the NCN 4 in this area.
I have found in wiki that route=bicycle defines "named or numbered or otherwise signed routes". Wouldn't people expect some markings on roads, if they find a route on a map?
Has anyone experimented with this kind of tweaks to routing?
I have tried to make different routing overlays for different activities. It is not easy, since Garmin defines many new activities, which aren't supported by mkgmap. I think currently only car mode allows for tuning of routing by changing route class and speed. This way you can get more suitable route but usually with wrong ETA. -- Best regards, Andrzej