All my suggestions relate to the review process in economics, in which papers are submitted in an uneditable format (currently pdf) and referees submit reports in the same format. No one directly "edits" the paper until it is in copyediting.
- Author: When an author submits a revised version of a paper, she should be able to submit also, in separate files, responses to the referees' and editor's comments. She should also be able to submit additional "supplementary" files.
Editor: The editor handling the paper should be able to designate which of the submitted files are visible to which referees. (I realise this is complicated, but the OJS team hasn't shrunk from complications in the past!)
Referee: A referee of a revised version of a paper should be able to see her previous report(s), the previous reports of other referees that the editor chooses to make visible to her, and the responses to referees submitted by the author that the editor has made visible to her.
(This suggests to me that a "file visibility" table that records which users can see which file is needed.)