I finally got the blocks going for playback on the WM8731. Between getting the asynchronous FIFO and I2C blocks working and writing the Arduino code, it took longer than anticipated but hopefully I've learned from my mistakes and updating the WM8731 block to read the D2A will go faster.

Right now it's still a lot of wires and breadboard but I'm planning on pushing updates to the WM8731 block and an Arduino example sketch to the repository tonight.