I wouldn't use Scribus for such a task, have a look at for example Multivalent Impose. You will then have to take the step of printing the text file to a PDF, and then Multivalent Impose to lay out the pages according to the imposition scheme.
I think the command would be like
tool.pdf.Impose -dim 2x4 -layout "7u,6u,5u,4u,8,1,2,3" input.pdf
Googling I found out that there is already a pdfjam-pocketmod, if you have a machine that can run pdfjam.