Disuse, abuse and the likes shall never forbid the use. I do not complain at Gaeilache and Tidonanatae yet I never used them, Gaeilache especially. Inmost campaigns armies tend to reach a standardised degree that means many players make use of a small percentage of the overall units available. What use is there in training Myrcharn if Curepos are avaiable on the same place? What use is Gaeilache if you can just recruit Gaeroas?

The fact that a faction is not often played, or that units are rarely used, does not by any means preclude their historical existance in the game. As for the Augustans I'm very sure the historical arguments are overwhemingly convincing for their existence inside the EB timeframe, so regardless if few people ever bother to reach the Augustan Reforms that alone should get them into the game as much as the Galatian Naked Fanatics and Gaelaiche and the thousands of steppe HA's with little difference among themselves. That and many others.