Together with a friend we've been using Native Instruments Reaktor for a long time. As a result we started building our own synths and effects a while ago. I am the one creating the concepts, think about functionality, etc, and my friend does the more complex programming stuff.
So i've been thinking.. Why not offer producers all over the world the possibilty to have their own custom built Reaktor Synth? You could really focus on what type of synth you want, how deep you want to go with programming, your own graphics, etc etc.