Did you look at this plugin? - Dynamic Action Plugin - IR Plugin Package
It's not for Classic, but maybe it can help you or you can just go with an IR report.
I think your idea of cloning the headers is right on track. You'll need a margin to offset the rows so the header is not on top of them. or better yet, add another div to spec it out and it's contents have the overflow set.
I know I've seen this solution before, just not sure where. it did take a lot of JS code.
Thank you for this Link. I've implemented this succesfully.
I have exactly the same problem - could you tell me / us your solution please?
I'm using this solution which was mentioned a few posts above: http://dbswh.webhop.net/apex/f?p=BLOG:READ:0::::ARTICLE:303800346302715