Itamar Tzadok

We have Group Peer Review activities with 3 phases: Presentation submission, Peer review, Presentation revision. In the Presentation revision phase, groups can access the reviews submitted by their reviewers and use them to revise their presentation and submit a revised copy.

If you have Moodle 2.8 you can try the approach described at Personalized access to course activities/resources. The general idea of the approach is that activities are restricted and unlocked for a user by adding entries for the user in a designated Dataform activity. For your purpose you need a variation of the particular application described in the linked thread. First, instead of adding the unlocking entries on behalf of participants, you can let your employees add their entries to unlock the activities. Second, you can set the Dataform activity to an interval, say 4 days, and max entries of 1. This will allow your users to add only one entry every 4 days to the effect that they will be able to unlock only one activity every 4 days. hth

That's life, isn't it?

In the Dataform you can have grouped entries such that each member of the group can edit the entry content. If the content is a document, then each group member can upload a document or replace the current document in the entry with a new one. Experience shows that groups still designate one group member to upload the group submission file. If the submission consists of multiple sections groups may sometime designate different members to upload/enter the group work into particular sections of the group entry.

I don't know about restriction by negative grades, but if you can use addon modules and you have Moodle 2.8.5 you  can try the approach described at Personalized access to course activities/resources.