in germany scooters are not allowed to use trunk roads. Kurviger has support for "not using speed roads" which seems to does the same.
My question would be: It seems quite easy to add your own VehicleFlagEncoder. I don't want to create a full navigation-solution but hope for more and more software to support this kind of routing, since it isn't currently available in any navigation-solution for iOS/Android that I would be aware of. Would you be interested in having more FlagEncoders in Core, or do you want to stick with the very basic ones?
Tbh: I don't know about the legal situation in other countries. I think that rule is the same for all EU-Countries. Scooters are limited to drive 45km/h and trunk roads require the vehicle to drive 80km/h minimun.