So, I like some of the #40K lore, a lot of the older stuff, but I like it more in concept then implementation. Lots of factions so you can find the one for you. Different factions within humanity so you can base then of different historical groups.
However, I don't like how they are very focused on a few super-heroic characters, and how you have bad people and more bad people. Also how it has gotten more and more GRIMDARK.
So I've slowly been writing my own setting in my head, that has the concepts I like, but less of the bits that make no sense.
Also groups based on non-western military units. Why not base military units on famous Zulu, Sikh, Persian, Arabic military units, in the same way 40K has WWI German, US in Vietnam, British Para, etc units?
so the first thing I wanted to do is have to human factions that were not obviously Good and Evil. because I think that's limited 40K somewhat in that if chaos is evil ,people conclude that the Imperium must be good, when it originally came here and was supposed to be just another evil or grey faction.
so one of the ways I'm going to do this is faster than light travel is done by a network of warp gates. An early conflict with one of the other major factions goes badly and they have to retrieve abandoning a critical now of the network dividing their empire into at least two pieces that can't communicate or interact.
@Canageek when the humans are divided up some of their major political leaders when one side of the network but the major political center was on the other. since then both of them have had elections and when they're reunified both claim to be the legitimate government.
Sorry, was playing #gurps for a few hours.
@Canageek I figure the human military has three tiers.
3) Normal troops. These look like troops you'd find on the battlefield today, but with better gear.
2) Elite troops. These are the guys you see in concept work on what real soldiers will look like when the next few technological advances come along. They aren't necessarily Special Forces but they're used as hardened units for special deployment to critical positions.
@Canageek finally the most elite tear are genetically modified and enhance soldiers, that are functionally immortal and only a small number are raised by each planet or nation. these are your Elite Warrior monk types, though the form they take is heavily cultural dependent from Warrior Monk and logs to Three Musketeers style swashbucklers two units based off other historical periods in Earth's history
So, you have two culturally very similar human nations, with lots of split families, military units where half of the unit was on each side, etc. Also since it is a very low key conflict it hasn't gotten really nasty. More of a 18th century limited warfare. So some units will fraternize across lines, there is cross-nation smuggling, lots of spies, etc.