The problem being that the junction isn't really suited to the role. As Labour found out when they pushed for Braypool and Horsdean - there was a lot of opposition - partly because it was wrong to tarmac over playing fields and allotments as well as making people lose their homes. Their eyes...
It's not really a park and ride though. There just happens to be free parking on a normal bus route. You could go and park in Patcham for free and catch a 5 or 5A or even park in Hollingbury for free and catch the 5B - I don't think anyone would call that park and ride.