1 - Quick question, why is there no ability to have people review the register of requirements like there are for the other documents?
Please note that the register of requirements is not in fact a document, but a list of entries referring to laws, regulations, contracts, and other legal requirements, where each entry can have its own frequency of review (because their deadlines and changes are not defined by the organization) and responsible person, so the application of the review and approval flow used for other documents does not make sense for this register.
2 - Also, same issue with permissions again. Only one person can work on this doc at a time.
At this moment Conformio does not allow collaborative editing of documents, so to maintain document integrity, only one user can be the document owner. During the document review, the customer can use the discussion tab to involve other users during the edition step. As a workaround to this, you can create a shared account and document who is allowed to use it and for which purpose.