How to make data management plans machine readable?
I think that one of the optimal solutions to the problem of "achieving machine readability for data management plans" could be as simple as specifying procedures of data conversion from source formats (human-readable or semi-machine-readable) into desired machine-readable formats for further data analysis. Those procedures might be coded in natural language instructions or, alternatively and preferably, via algorithms for benefits of automation and reproducible research.

Conversion from machine-readable formats to human-readable is an optional step, based on projects' requirements (while optional, this is a typical step for most projects, implemented in their reporting phase). The types and details of data conversion functionality IMHO obviously depend on projects' specifics and, therefore, should be determined and specified on a project by project basis.