Thanks, this is a good suggestion. I would be happy to use it.

I honestly don't care what you think. You are not familiair in the area, have not micromapped it, and the tagging is part of the openstreetmap database, and has not been used in rendering profiles.

I don't care about scores too. It seems you are only trying to formalize tagging, but don't come with solutions for routing in these situations.

OpenTripPlanner, RoutingKit, probably any router that can be configured to use tags.

Exactly. The surface is a field of grass used for camping. While passing the surface in the middle moving to another campingfield is a highway activity. Don't want to render it on the map, do want to route over it.

The hole purpose of having added these tags is the ability to route pedestrians over the camping place. Hence the highway tag is used on surfaces which form a graph. The highway=grass is not rendered. Don't do any harm, in the database, and should have been implicitly followed, sadly the OpenStreetMap routing suggestions do not map implicit things, thus they must be made explicit.

Because there is no road.

No, highway=grass.

Nope, it is a routable surface, not a footway.