I know that tagging for the renderer is frowned upon but how about changing the real world to match the renderer, which is what indeed appears to be happening to the national cycle network over in Derbyshire…

“It has come to our notice after studying both Sustrans and Open Street maps, that numbers of the NCN Routes on the ground in the Etwall area differ from those on the maps. This is the result of stretches of new routes being built piecemeal over the years.

…

This is a far more logical way to number these routes, so we are proposing to change the signing to agree with the maps. “

http://rangersderby.blogspot.co.uk/2014/08/local-route-re-numbering.html

(Now watch the map change to match current reality until the signs are changed :p )