since 0.17.10422, PartDesign::FeaturePython object is available for making custom python features for PartDesign workflow!
So all the awesome python workbench developers can now start flooding it with cool features!
I also invite you to drop a link to your workbench/macro if it uses PartDesign::FeaturePython, right here!
A word of warning. PartDesign is still evolving, so there is a high chance that you'll have to update your macros/workbench later. Also, more py bindings are required for deeper support (such as use in pattern features).