I agree with the others, an Arduino driven Fatman synth sounds like a great idea. 
I was planning an Arduino based TB-303 / x0xb0x clone shield but I've been put off by how difficult it is to source the original components (mainly the transistors). So instead I've been looking at the Paia's Fatman or the Voice of Saturn as an analog section with the Arduino providing the digital section.
Let us know Paia's response.