Currently, an inherited DropDownList widget can only bind to another of the same type  or another vanilla DropDownList (via  alternativeNames array at kendo.all.js line 32813) 

A use case is that I originally created ParentCustomDDL and ChildCustomDDL with the intention of cascading from parent -> child. Since alternativeNames is hard-coded, I was forced to merge the code into one clumsy widget so that name matches name.