You'd think that switching from 18th century firearm formations back to Roman Legions would have forced them to refresh.
They did not.
I'm playing Rome 2 (Emperor Edition) right now. Some new features off the top of my head that aren't present in any of the other previous games:
Province/Region system. Adds a new dynamic to conquests and an incentive to conquer certain regions over others. Shared resources and abilities over the entire province. Ability to enact edicts if you own the whole province. Culture, in particular, is heavily affected if a province is shared between two or more factions.
Imperium mechanic that determines how many armies/fleets/agents you can recruit, as well as various bonuses and penalties for each level. Makes each army more meaningful.
Recruitment mechanic that reduces micromanagement by having the general recruit directly, based on the province he is in. Ability to levy from client states. And you don't NEED to have a bunch of small armies anymore, because...
Garrisons that actually matter, based on the advancement of the settlement.
Ability to split military buildings into either faction recruitment or auxillary recruitment chains, with the province determining what units are available on the auxillary chain. Greatly increases unit options. This one was long overdue.
Amphibious battles.
Armies and agents automatically creating their own transports when crossing sea instead of having to have a fleet waiting for them.
Ability to control forty units in battles with reinforcements.
New "three traits" system for all characters, including agents, which allow a lot of different abilities. Lots of different things your agents can do now, all of them logical.
Stances. Forced march in particular is very useful.
Diplomacy that works better than in any other game previous.
Split of alliances into military and defensive, with military being harder to get.
Client states and military allies actually counting for province victory conditions, meaning you can achieve victory more diplomatically.
Political system based on the gravitas of your generals, which in turn is based on their accomplishments in the field. Various political actions you can do to gain more influence in the Senate (or other faction equivalent) which has its bonuses. Threat of civil war based on how high or low your influence is.
.......
Like I said, this is the recent Emperor Edition. I didn't play it on the original release, though I've heard there were a lot of problems. If most of them weren't fixed until the Emperor Edition, then that should have been the initial release. Still, if it was rushed, that's a publisher problem. Bugs, in particular, are the responsibility of the publisher.
Anyway...
Don't know much about Warhammer, other than that it's basically "fantasy races in space"...right? How large a role does magic play in this universe? Can we expect wizard units on the battlefield?