A communications system may include a plurality of data storage devices each using at least one of a plurality of operating protocols. The system may also include a plurality of mobile wireless communications devices for accessing the data storage devices, and each may use at least one of the plurality of operating protocols. Furthermore, the system may also include a protocol interface device including a front-end proxy module for communicating with the plurality of mobile wireless communications devices using respective operating protocols, and a protocol engine module for communicating with the plurality of data storage devices using respective operating protocols. More particularly, the front-end proxy module and the protocol engine module may communicate using a common interface protocol able to represent a desired number of protocol-supported elements for a desired operating protocol.