Hi,
I'm the Mobile team leader, thanks for your suggestions and feedback (and for opening the issue in the tracker).
Certainly, the lesson module is the most requested one (of those missing in the app), in the last Moodlemoots we did Mobile Workshops and the participants voted for the lesson module too.
I did an initial evaluation to evaluate how difficult would be to implement it and I noticed that the current code will require a complete refactor, moving code to new functions/APIs that can be exported via Web Services so the mobile app can "communicate" with Moodle.
It would be a lot of work but I think we would be able to do it, I see it difficult to land in Moodle 3.2, but Moodle 3.3 sounds reasonable.
Regards, Juan