Implement VersionPress as part of your WordPress Toolkit. It uses WP-Cli and is Open Source.

By contributing to the project and having other devs already working on it, you will be able to amplify the speed of work being done.

Further, this project is the holy grail of WordPress development. People would literally flock to Plesk for this feature alone (not to mention its awesome in other ways).

Please seriously consider contacting the VersionPress Team. This Project basically takes the idea of Git integration, staging, and data syncing to the next level. Database changes are checked in to Git as text files where you can then resolve conflicts... you can literally edit the same post on two versions of the same site, and then merge the changes from both.

This would be a huge boon for Plesk and it already aligns nicely with the WordPress Toolkit... since it uses WP-CLI, you could simply make a GUI for it and help with the core code to speed up production.