How to create choose your own adventure of select x activities of a possible y with only x graded?

Background: I am assisting with creating a Brightspace for a summer research internship program. The course requirements are more of a completion mark than a grade. Students who complete the course activities receive a cocurricular record credit (extra-curricular activities that wouldn't appear on an academic transcript). These activities are designed for meaningful engagement with the program, to provide some soft skills training, and sharing what students are working on with their research supervisors.

Students are required to complete 4 professional development sessions, either synchronously or asynchronously. Asynchronous sessions are hosted via Voicethreads. I have set up the Voicethreads, they are connected to the grade book,

Issue: We have over 15 Voicethreads students can select from for viewing as their required 4 sessions. Only 4 need to count towards the grade. These are a pass/fail mark. When I set up the gradebook, there doesn't seem to be a clear option to say only take 4 of all possible grades for this activity. We need an easy way to see if someone hasn't done their required 4 sessions as there are over 300 students in the program and at most 3 staff members supporting the program off the sides of our desks. We don't care if they do more than the required 4 - great for that student who chooses to do so. It's a "choose your own adventure" completion mark, rather than a required grade.

Question: Is there any way to set up a grade book like this? Only count x of y completed activities towards the grade? Ignore all other submissions? Our internal helpdesk has suggested setting these up as "dropping" the 11 (or more) activities, only counting 4 towards the grade. All non-counted activities will be set to 0. The grade book will need to be set so that all ungraded items are set to 0. I will be trying this today and asking some colleagues to test this set up. Is there another way to set this up?

I have taken courses through another LMS (whatever is used by Mohawk College's Continuing Studies). Their system offers this kind of configuration. I can imagine others wanting to give learners options of what to complete but only have their chosen activity count towards their grade. It would be great to see something like this implemented in the Brightspace system.