You've made some very excellent points here. Perhaps a good explanation and reminder as to the similarities was what I needed.
Thanks

I didn't actually make the connection between the pre-Marian Republican Legion formation and how Caesar deploy's his forces. Is there indeed indication that he uses the hastati/principes/triarii deployment? Obviously in practice one doesn't see it because you can have Veterans attacking before recruits and such, but this is simply a result of game mechanics. So my question is of course based more in lore.
Oddly enough, Chief Hanlon is the only character that explains this (as far as I know at least) as I've never heard any member of the Legion say anything about it. Somewhere in his long-winded dialogue, he talks about how the Legion sends a wave of recruits first, then the primes, then the veterans. I think he says it if you ask him about the First Battle of Hoover Dam, but I'm not sure.