you read my mind, as I am working on the "delay" settings at the moment.
It will be possible to specify the length of delay that the quiz waits before returning to Moodle. If you specify the delay as zero, then the quiz will not return to Moodle, and the student can continue to play with the quiz, and then navigate away from the page when they feel like it.
I haven't started work on it yet, but during March I hope to make it possible for students to review the previous attempts in the context of the quiz (at the moment they can only review their answers on a page with a completely different format to the original quiz), and also resume attempts - much like the Quiz module currently allows. This will be rather tricky to implement though, so I will need a lot of encouragement
Thanks for the offer of being a beta tester.