The BDBHPT driver has been optimized to provide the best possible performance a DLZ database can while still storing the DNS data as text (ASCII). The largest remaining performance impact in the BDBHPT driver which could be eliminated is the query-time conversion of text to Bind's internal data structures.
The Berkeley DB can store binary data just as efficiently as it stores text. It may be possible to store Bind's internal data structures directly in the Berkeley DB and thus eliminate most if not all the query-time text conversion. Instead, the text would be converted to Bind's internal data structures when it is added to the database. This could allow DLZ to very closely match standard Bind's in-memory performance, while also providing all of the benefits of DLZ's immediate updates and simplified DNS management.
In addition to the driver, either a command line database management utility like dlzbdb or a replication solution would be necessary.