It would be much harder to print through the base of a paper negative, and I'm not a fan of oiling/waxing a paper negative to make it transparent. Ortho-Litho film is a great way to make enlarged negatives, but going via the interpositive method (print to positive, then contact print for a negative) increases contrast unless you use some soft-working developer for the interpositive. Rather, you can try to make enlarged negatives by reversal. Ed Buffaloe has a fantastic article on it at Unblinkingeye:
I have personally tried this method for a variety of print films that I have, and also on some X-ray films. Although there are some variables and you would have to mix a few baths, once you get the process tuned, making enlarged negatives becomes a fast and economic process.