Hi Paolo,
Currently I only have the basic plugin. This has seen the removal of being able to grade assignments in Moodle leaving staff with having to create a separate assignment to mark. This is unworkable in the long run. I'm also concerned with changing in audit requirements that I may require us to have a copy of assignments stored on the Moodle install and not just have a copy at Turnitin. Currently that would require us to have two assignments, one to submit to store and grade, and then the Turnitin assignment for a similarity report. Again, confusing and not very helpful.
Your solutions looks ideal, and I have used Dan's beta plugin for testing in the past, but was somewhat concerned that he wasn't able to actively develop it. The guy's gotta eat after all. Dan's an awesome guy for doing all the groundwork, and an all-round good guy too .
Anyway, Dan's alluded to some new developments with Turnitin in the near future, so I may have to wait and see what becomes of that.
All courses where I work are required to have a Moodle presence, and most of those now also request electronic submission of assingments. We've added Dropbox and Google drive to assist staff and students who use iOS devices. Some teething issues there with timeouts, but there is a tracker item for this, and a simple workaround.
Keep up your great work. Your assignment interface is certainly a work of art. So much more user friendly than the current 2.4 (well that's my opinion, others are obviously free to disagree).
Cheers,
Adam