Thanks for the enhancement request. I'm sure your support will help furthering the issue.
I have one question about your proposed solution. Do you see any downsides to automatically attaching <thead> to every report? No doubt your generic solution is the best, but if changing the report template structure is too big of a change (at least for the next 3.1 version), maybe, as a starting point, the printing engine can automatically embed the <thead> in every report.
But after thinkg and try somethings for a time, I try this:
- In the Report template put in before rows section: