I will shortly provide more full documentation on the website on creating custom graph systems along with their nodes.
Regarding specific node Input and Outputs, I’ve already done some work on that when started creating the codenamed “MX” system which will work similar to Softimage ICE or C4D xpresso (although simpler).
This is of course made on top of NodeCanvas and I think for what you are after it would be a good starting point to work upon probably, since it provides specific Input and Outputs to work with.