Connected Bluetooth Device Not Recognized as Audio Device
Resolution:

I installed Yosemite on an external drive so that I could find all the system files related to audio (using EasyFind, a great search utility for Mac), compare them to my existing system for any file size mismatches, and then replace the offending file(s).

The offending file was found in /Library/Audio/Plug-Ins/HAL and was most likely "BluetoothAudioPlugin.driver" (duh), though I replaced all the files in this folder with the system defaults, so I don't know that it was solely caused by this one alone.