[eluser]Majd Taby[/eluser]
Given your deadline, Here's what I would do:
1) Modify the one-to-many plugin so that you can add your own WHERE clause to the query through YAML. The changes to plugins/onetomany.php and plugins/relationalcontainer.php should be minimal.
2) As far as editing, deleting, you're correct, CodeExtinguisher doesn't support that, but now that you mention it, it would be a very nice addition. I can't promise you I can deliver on it on a week though. As an alternative, you can modify the RelationalContainer::getHTML() method to add a link that takes you to page to manage the related data.
I know it's not an optimal solution, but it works and if it's an option, you can update your clients' codex setup at a later time.
