Its curious you should mention using audio input as the method for data control as the very first prototype (some years ago) initially used such an interface.
Unfortunately such a solution ultimately complicates the process rather than simplifies it. USB, serial and Bluetooth are bi-directional for example, and not all phones have mic inputs.
There is, however, a possibility related to this.
Assuming the Quixote comes packaged with an onboard computer, be it complex like a Raspberry Pi or simple like an Arduino, one could imagine using the mic inputs on these to be fed sound from a radio broadcast in much the same way as computer programs were distributed in the UK during the '80s.
Thus reading material could be distributed to areas of the world without reliable internet access. Perhaps local BBC World Service stations could use quiet periods during the small hours for this. Assuming a *very* conservative 1,500 baud, which could likely be bettered by a factor of at least three, an entire novel could be broadcast in ten minutes, or one short story a minute.
So, yes, good idea!