The module isn't very old old, and the author seems active, so I don't think there will be any issues with getting in touch with him. Trying to maintain maximum compatibility with the existing module will absolutely be a high priority if I OO-ify it. The more similar it is, the easier it will be to maintain and use.
Just to clarify, you believe the best option is to integrate the OO interface into the same module as the procedural interface, and not to put it in a separate package? Any particular reason or advantage for this, or just personal preference?
Note: I'm not disagreeing with you, just trying to clarify my understanding of the best way forward.