Colour displays nowadays draw just a tiny bit more power than old B/W LCD's, just look at all the new colour cellphone displays.

Bluetooth would not be suitable for the main (initial) sync of the device, but would be perfect for adding the few songs you do a day, just setup so that whenever it detects it's base it grabs all the new music waiting for it, or transfer playlists with friends, plenty of possible uses for it. WiFi would be even better but would be a major battery drainer and a hassle to configure with just a jogdial.