The benefit you would gain by using this approach is a greater level DR. Shared storage in QlikView is presented to Publisher and QlikView Server as windows CIF share (the only supported approach).You could move QlikView applications, QVD's and PGO files along with config files to the share. Therefore, if you were to experience a failure and you had a cold standby machine available, the DR machine would reference the shared storage instead of local disk. The SAN is more likely to be backed up regularly.
To ensure the storage on the SAN is not overloaded, you should separate your QDS and QVS shared storage.
Most customers, who utilise shared storage for clustering purposes, as you mentioned. We recommend a windows virtual file server is attached to the SAN and your shared storage. The windows file server presents the shared storage to QlikView as a single UNC. You can cluster the windows virtual file server using 3rd party clustering, to increase resilience within an architecture.