I feel it should instead be treated as a residential street because currently it feels too hostile to pedestrians & cyclists.
Unfortunately this might not really help much.
Cranston Road is unclassified but is on the junction with the south circular & Brockley Rise. As such cars & commercial vehicles see it as a through route to Bell Green Sainsbury's and drive along it accordingly.
This is clearly a residential street and the traffic is horrendous so I don't see much hope for declassification and improvement to the road from One Tree Hill down through Honor Oak Park.
I agree with your points entirely though but feel very pessimistic about the council doing anything to resolve any of these matters.