well we are talking about little DLC's and not Huge Expansions....you may be right but the truth is we only buy such product just so we can make a great mod run,which in its essence is we don't care about the Expansion itself because all we need is its function to make a mod work.........i just hope CA don't follow the Steam Bandwagon,Steam eats resources and also make a lot of things slower compared to having your own servers and multiplayer functions,the only success game that is suitable for steam is games like DotA 2 or other F2P games.
But anyway good news guys because it seems Rome 2 is too customizable enough to satisfy your needs and in addition to that the developers have put modding in mind and they have built in mod manager or mod kits as i see it in some pictures and videos.