I think it would make more sense to reduce the timeframe. Let it run from 272bc to the Marians (or whatever), then do a second campaign starting roughly when the first ends.

That way you could have factions that are "questionable" in 272BC (Parthia, Bactria) in the later campaign without bending the truth.

You'd get around one of RTW's Achille's heels, the way the the "barbarian" factions don't learn (e.g. to build paved roads) as they become more urbanised.

You'd get around the game starting to become boring after you hit 30-50 provinces and the opposition turn into speed bumps, and the distance to capital penalties cause more difficulty than the enemy.

You'd mitigate the disconnect between the actual history that the EB team privilege and the alternate history that players create in the game by reducing the scope for factions to expand non-historically.