This functionality is surely one that needs implementing.
Restricting users to only view certain contacts isn’t a viable alternative, they still need to be able to edit certain basic contact details but we’ve created custom properties that we would love to be able to lock from editing by most users.
These custom properties form part of our membership information (including subscription due dates) and if changed, would result in potentially issuing invoices at the wrong time or not at all.
The current permissions functionality is to high level, basically, all or nothing which I think really needs to be reviewed.