The goal of a realistic interstellar mission to the nearest star recently announced by NASA as a new space exploration objective targeted for circa 2069, presents a daunting but exciting prospect for creating a pragmatic but visionary mission design. For such a long-range mission goal, mission enabling technological developments need to be developed and evaluated in precursor missions beyond the edge of the solar system. NASA is stimulating such a pathfinder mission starting this year to promote efforts that could build upon what has been accomplished by New Horizons, and for which APL can leverage heat shield technology used on the Parker Solar Probe. An academically-inspired graduate-student supported study at Johns Hopkins University reported on our progress presented at the 2018 Committee on Space Research meeting (COSPAR 2018) in assessing and evaluating several critical subsystem issues and fruitful lines of innovation to improve dual-band downlink performance for a 1000 AU (1.5 × 1011 km) mission. This work recapitulates and extends some work done much earlier at APL. We propose to quantify several critical subsystem trades essential to interstellar spacecraft communications, command and data handling, and critical guidance, navigation, and control (GNC) functions. These include the following: optimizing trajectories during transit and arrival in the targeted system, acquiring a quality mix of relevant highly-compressed scientific data, providing an accurate navigation capability at sub-relativistic speeds, insuring a robust communication system over extraordinary distances, and maintaining an effective command and data handling subsystem, while acknowledging the criticality of a survivable spacecraft bus in an illdefined, harsh and very long duration environment.