Offer a hard drive option to store music within the car.
Have a built-in hard drive to save music from a USB. This could then link to a search tool, perhaps even by voice control, to make accessing the music you want much easier if searching while driving.
Moderator: Tesla originally had this as a planned option with the internal flash drive. As they added features, it left little room for such a feature. Not sure what the objection is with using a USB drive, where you can pick the size and easily add and remove songs using a PC without dealing with a complex car interface. You can even add an SSD drive to store your music via the USB port.
(lightly edited by moderator)