Got mine today, looks real good. Nice job with the instructions too! I will hopefully get to tangle with it over the weekend, depending on what the weather does.
As for the universal board, it may be possible. All the inputs (CD, FM, AM) run to the same place, and it's just the absence of two of them that allows the third to play uninterupted. If you could trick the radio/CD (or radio/FM or radio/AM) to both think the other is hunky-dory, then it would work. The thing is, that info gets passed along a data bus, so it will take a bit of deciphering to figure out.
Craig