I'm typesetting a book using dblatex/XeLaTeX that will be printed 2-Up on 8.5x11 paper (double sided), then cropped to a smaller size and bound. I have external tools to take a pile of 5.5x8.5 pages and splice them together in the right order. The goal is to minimize the number of stack cuts and to use the factory-cut edge for what ends up being the outside and top of the finished book, which means that the logical pages need to be flush left for left pages, and flush right for right pages.
The only way I've been able to make this work roughly the way I want is to specify the physical paper size (5.5x8.5) as the paper size, then specify a very wide inner and bottom margin.
The only problem with this is that I'd like to be able to insert crop marks, which requires setting the page size to the logical page size. When I do this, xelatex flushes both left and right pages to the left—that is to say, the area outside the logical page size always has a wide margin on the right side regardless of whether it is a front page or a back page. This means that if I actually printed the document two-sided and cut the pages, I'd get only about half of the flip side because the front and back would not line up correctly.
I've also looked into a couple of packages that are supposed to make this easier, but thus far, they all seem to operate under the assumption that logical pages should be centered on the physical page. Although that makes for reasonable looking output for draft purposes, it's wholly wrong for actual printing because instead of having to cut only two sides, you now have to cut all four. And if your cuts aren't exactly perfect, four-cut production results in a fairly significant amount of non-squareness.
The packages that allow you to offset the pages from the center, if the descriptions are to be believed, always do so in the same direction on all pages, which makes those similarly less than helpful; to do it right, I'd need to specify a positive offset for odd pages and a negative offset for even pages.
Which brings me to my two questions:
Are there any packages that provide full control over how logical pages are oriented on a physical page (separately for left-facing and right-facing pages)?
Is there a good way to draw lines at a specific absolute position relative to the top left physical corner of the page, entirely outside the scope of the text/content flow, without regards to any margin settings, and with different content on left and right pages?