The following documentation section
contains more details on how custom widgets can be created and custom behavior can be achieved by extending the Kendo UI widgets.
As for whether the particular requirement you aim at implementing can be achieved by extending the DataSource and overriding the existing functionality, this we cannot confirm or deny. The Support Service provides guidance on built-in features, while custom implementations such as the one you are after fall within the scope of professional consulting that can be provided by our Professional Services. They can perform the research required for answering the question whether the customization in question is possible, and can provide guidance or assistance with its implementation, if such is needed. In case you are interested in our colleagues' services, let me know and I will put you in contact with them.