I think a nice addition to the parts list would be a resizable dish antenna. The most visible part of unmanned planetary spacecraft is the large dish antenna. Apollo spacecraft had dish antenna. I use interstages in the Soyuz style for my antennae. The problem is placing that antenna in the very last stage so I don't eject it prematurely.
Not only resizeble...but you are right, the probes are 85% big antennas.
It would be fun to send probe with near range antenna and orbiter with short range reciever and huge dish relay antenna.