Battania does have archers (some of the best in fact), they're just on the "noble" troop tree and are a lot harder to attain.
The two ways are currently to "reliably" recruit them is to find them in prosperous Battanian settlements or capture, recruit and upgrade forest bandits (with disciplinarian perk at Leadership 125).
That said, having them a bit more commonplace or a weaker version in the basic tree would be awesome.