Well I got the borders to disappear after fixing a file in reportlab, as described here: https://bitbucket.org/rptlab/reportlab/issue/29/platypus-frames-showboundaryvalue-no
It seems that the fix isn't yet officially released, I don't know.
Now I just need a proper styling and then maybe a simple GUI for downloading xhtml2pdf and reportlab, then I will release it as a single workflow for editorial.