Keep in mind that although it is unfortunate that they didn't let RUN use Torcleaver, Ragnarok and Caladbolg aren't particularly exceptional great swords. Aettir (for pure tanking), Macbain (DD-focused), and Humility (hybrid) are all good non-Ergon weapons.

Given the current disparity between sword and great sword weapon skill potency and /NIN's status as the typical go-to sub, you can instead work with the current situation and just dual wield swords.