You can add or remove people on an assessment at any point while it is being worked on, so a colleague can be brought in to complete part of the form and a departed contact can be replaced without reissuing anything.
In Brand Cloud the list sits on the “Sent to” card with an Add recipient field. On the supplier's form there is an Invite collaborators button in the header. Typing an address offers the supplier's saved contacts as suggestions, and a new address is remembered for future assessments.
A newly added person is emailed a link and signs in with a code sent to their own address. Granting and revoking each ask for confirmation naming the exact address, and every change is recorded in the activity log.
Everyone on an assessment has equal rights — they can read, edit and submit it, and add or remove others. There are no view-only invitations. Once an assessment is submitted or cancelled, no one new can be added, though existing people can still be removed.