Dear Arya,
As per the process the coding mask of WBS will be defined by the PS module itself, but that WBS no will be shared to SD team for booking the Revenue of that particular project WBS. If we want to restrict you can develop validation from sales point of view by mapping Sales order with one project /WBS range.
But as per the PS point of veiw there is milestone Billing functionality ( DIP Profile ) has to be defined and to be integrated with both project and Sales order, for PS & SD integration .
And through CNS0 is for project delivery.
I hope it might be helpful inf.
Regards,
vrkumar