So, there seemed to be a lot of back and forth about this, but if you read the following closely it appeared to be possible:
https://www.reddit.com/r/project1999...on_kos_update/
https://www.reddit.com/r/project1999...final_numbers/
https://www.project1999.com/forums/a...p/t-82203.html
I just thought I'd throw it out there that this does indeed work. Faction continues to update after Legion maxes out. I started at Amiable to Legion, and 507 stacks of bone chips later; I'm able to vendor in Cabilis (was able to bank after about 375). I think I hit apprehensive to the SKs, Shaman, and Residents at the same time, at just after 2500 turn-ins (probably 2501, but I checked at 2537).
Now, to work on the Necro faction...
For the record - Human Cleric following Mithaniel Marr.
-Mcoy