This is probably the easiest route envisaged. The surface of this route was envisaged to be proper ashphalt that could be maintained and used 24/7 12 months a year. The Valley Trail would need to be resurfaced and widened to allow for a 2.5m segregated cycle track alongside a footpath for the whole of the route to Rodbridge Corner. If possible and eventually this would need to link with route RC-RH from Rodbridge Corner to Rodbridge Hill.
There would be various feed in routes such as from Middleton Road across the meadows on existing routes.
Currently this route is unusable from October to March and for the rest of the year after any heavy rain. (it is usable by full suspension mountain bikes but not by Town, Road or Hybrid bikes or Mobility Scooters).
Nobody I have spoken to about this has any objections though joggers would rather the surface was not black asphalt as that would be too hot to run on during the summer months). It is interesting to note that the new canal side shared paths in Salford near Manchester utilise a half recycled tyre/half aggregate surface, similar to those used in playgrounds. This has advantages of better drainage and is suitable for cyclists, pedestrians and equestrian users. However this is only necessary on areas commonly used by equestrians for horse riding, elsewhere a taramacdum surface will suffice, this does not need to be black tarmac.
John Grimshaw, the architect of the Bristol and Bath Railway Path recently completed a path in Buckinghamshire, the turnout cost excluding admin and project Management was £100k per km, though some parts had no existing substrate (a hardcore base surface beneath), most of the route from Kingfisher to Rodbridge Corner does have an existing substrate so the costs may be lower in places, but some sections are also prone to flooding so will need more work and thus costs may well balance out.
Ideally the first stage would be to draw up technical plans and a project plan put in place. John Grimshaw advises this could be done by the Campaign with the advice of themselves and Sustrans. This would enable a fully costed plan to be drawn up to enable funding to be sought.
Dog walkers would probably have to be more alert or keep their dogs on shorter leads as if the effect of putting a new surface on the Valley Trail is as envisaged, there will be be massive increase in cyclists using it.
Finally, when the bridge at Bakers Mill is complete it would enable the Valley Trail to be extended to Great Cornard. This would have I suspect the greatest impact as this is the busiest road for commuters from Great Cornard who work in Sudbury.