You could get the macbook air USB optical drive too. It has the same length and width as the mini, so it should look fine sitting on top or below it.
Quote from mcifix:
I hadn't noted the loss of the microphone port. Arghhh. Tradeoff to get firewire back is worth it, but still very unfortunate for some folks.
I'd just use a USB microphone. The rockband one's are actually pretty nice.