There are barred and script letters in the same equation, so I definitely can't use script for my barred letters.
There are no barred letters in the same chapter as bold letters. That is, a chapter has bold vector letters or barred set letters, but no chapter has both bold and barred letters.
So, I think I'll use bold to represent barred letters.
I'll include a transcribers note in each volume explaining the use of bold in that volume.
Thanks for asking around, Katrina