My suggestion, if you need data level security, try to apply that in the cube through essbase filter (read or metaread filter). In your case say read filter on the essbase cube on cost center. Then in RPD instead of using generic user to connect to the cube use :USER and : Password
In that way you will not have to tinker with rpd identity management every time you pull cube in RPD. You have to do that every-time number of level changes in any dimension.