A not-so-ordinary Workflow scenario

The scenario: the project calls for 30 individual reports generated by different writers (some of the writers will generate only one report whilst others will be responsible for more than one). These reports are to be uploaded to the site from where they will be downloaded by a handful of reviewers, each reviewer being responsible for a specific set of reports. Reviews will be uploaded as documents which will in turn be downloaded by the writer and so on and so forth.

The twist/s: each item uploaded needs to be uploaded as a separate/new node until, finally, one of the drafts submitted is marked as "approved" (as opposed to reviews and revised reports being contained within one node). So, a View which displays the history of on report would consist of a number of draft report nodes and review nodes, all in sequence. Furthermore, each time a report or a review is uploaded, the relevant writer and reviewer need to be alerted via e-mail.

I have avoided using OG for this as I feel this is overkill and far too messy for something that I'm hoping can be handled by workflow or workflow-ng. I have, however, been working with both modules but have not been able to find a solution to the problem presented by the fact that action e-mails need to be sent only to the writer and reviewer in charge of a particular report. For example, if a reviewer uploads a review for report # 26, how will the system know that the action e-mail needs to be sent to the writer of the original report #26?

Any pointers would be greatly appreciated. Many thanks in advance.

p.s. the reasoning behind having all submissions as separate nodes are that I need to show a very clear history/overview of the entire review process. This needs to be EXTREMELY simple as most of the people relying on this system have very little computer knowledge beyond using Word and sending e-mail.