There was recently some discussion about Space Marine army lists at the Epic Forum. One of the posters commented that Space Marine armies would be rather simple to develop. And in a certain sense he is right. What difference is there, at the scale of Epic: Armageddon, between Ultramarines and Dark Angels? Or, as a better example, Ultramarines and Imperial Fists?
Part of the problem is that the background for these armies are developed for 40K which uses a scale and scope of gameplay that doesn’t allow for some of the armies to be fully explored. Some of the differentiating characteristics of various Marine Chapters don’t make a lot of sense for 40K which, despite the Codexes, doesn’t have much actual structure to the army lists. 40K is more of a skirmish game and it doesn’t have any way for the structural elements of the army lists in Epic: Armageddon to present themselves in as much as a meaningful way.
So if the 40K background makes allusions to the Imperial Fists being siege specialists this doesn’t actually, currently, get much exposure in 40K. This might change with the next version of the Space marine Codex for 40K but currently an Ultramarines army is pretty much the same as an Imperial Fists force.
Epic: Armageddon allows army list developers a chance to explore other options. Specifically it allows you to create army structures that influence gameplay as much as the units themselves do. So an Epic: Armageddon Imperial Fists siege army might have artillery companies, specialist trench attack formations or they might lose access to Thunderhawks.
Its these other options that make Epic army lists challenging to write and also open up possibilities for army list developers.