Excellent ideas! I record the violin lessons I teach, and send a file via email for their review. While working on preparing standard-rep pieces such as a Handel Sonata, I play continuo (accompaniment) on either mandolin, viola, violin or keyboards. I take the time outside of lessons to learn and prepare each piece well so that I improvise a little. As this was commen-place in the Boroque era, I’ve found its still am effective way for the student to become more confident in their playing, while still exploring the possibilities of the music. Once they’ve become more advanced/confident in their playing, I introduce scales and excercises, including the learning of transcriptions. One of the most challenging books out there is the Charlie Parker Omni Book (in C-Clef). I’ll be happy to elaborate more if someone has any questions. Thanks for starting a good discussion.