I actually prefer smaller maps too, though I am not sure which Roman-era mods have small maps. Most mods (often unwisely imho) tend to go for the thinking that bigger is better. "Gods & Fighting Men" has a small map (Ireland and the Isle of Man) but is set about 700 years before Rome even existed as a Kingdom

More mods with more focused campaigns would be a great thing.

Oh, just remembered, RTR has it's Iberian Campaign which is a small map - and that is Roman era.