A quick test has proved to me that org-conflict is able to do exactly what I want it to - in fact, it's much better than I had imagined, with useful features I hadn't thought of.
Now, if I turn out to be smart enough to make it run properly on all my Org files, I'll be extremely happy with the result. (So far, I've only tried the demo file provided by the author.)
If you want to test it, you need to install a single .el file, add 2 or 3 lines to your init file, and temporarily add the author's demonstration file to your org-agenda-files. The test is nicely laid out and simple to use, in a "Here, press this button and watch what happens" sort of way. (Not literally, but I think you know what I mean.) Very easy to remove again if you don't like it - but I do like it.