Oh yeah, I agree.
Hopefully they have a copy of
Bar-Kochva's The Seleucid Army on hand.
With the Successors in general, I'd like to see military settlements handled in an interesting way but that seems doubtful, the focus will be mostly on Rome I bet.
However, the increased focus on individual units might be awesome for the Seleucids. Their elite troops, such as the Argyraspides, were very important historically.
Successor warfare is definately going to fit into what CA is trying to accomplish, as veteran phalangites were prized almost like a valuable commodity to the Diadochi. It would be sweet if you could capture the troops of another Greek-culture enemy and, instead of release/kill/enslave, incorporate them into your army.
What immediately made me think of the Seleucids is CA said they might make weapon loadouts customizable for some units. Which definately would be historically accurate for many of the elite Seleucid troops.