I am sure this thread is already long enough in tooth...but.
Using oils on paper is quite an established technique, it even has a fancy French name "Peinture a l'essence" this refers to the oil being drawn from the paint by the porous surface of cardboard or what was/is called cartridge paper, first by Degas then Toulouse-Lautrec . Now, of course, Arches has produced a sized paper expressly for oils, so there may not be a need to size your own...though I have tried it and have found it's surface too smooth for my taste.
As had been mentioned earlier, shellac is probably the oldest (time tested) and effective way to seal paper as had also been stated, there is no use of water, shellac being an ethyl base.
Nice informative thread...there is not a whole lot of info about this in the general art biz genre!
I don't know about Degas - but i read a few years ago that Lautrec used to strain his oils through a gauze and wait for the oil to seep out - he then painted/drew with the residue which was an oily chalky paste hence his very drawn style and perhaps how he was able to "paint" on paper. I've searched for the reference but can;t find it. Perhpas the minimum of oil on a sealed paper was what Lautrec and Degas used?
"That Gutenberg guy" who is mentioned several times on this thread used linen-based paper (as well as parchment, i.e., animal skin) that was sized. In addition, the inks he used were more like our ball-point pen inks. (He didn't do any illustrations; those that survive in books from this period were likely done with watercolor). The paper in 15th c books (if it has not been washed, or subject to excessive wear) is probably not comparable to what we get or even think of as paper today. (That said, you can of course paint WITH anything ON anything -- if it doesn't last 500 years, so what? Most of Gutenberg's books didn't survive either.)