Army themes

True ... It would also have to include points for matched play ... Would have to make a section in the back of the codex specifically to house all the data sheets

If there's no kabal of the obsidian rose I'm gonna be powerful sad

Well if they go the route of SM each kabal, cult, and coven will have something like a doctrine a stratagem and a unique WL trait. but that would be a lot of different rule sets. Not to mention the army wide generic WL traits and stratagems. But they aren't exactly opposed to doing such. It'll probably be one page for each kabal, cult, and coven ... A page of generic stratagems, and a page with generic WL traits and relics on it, then a page of upgrades and wargear followed by updated unit data sheets. Then points values. Fluff will be the first half of the book.

The Imperial Guard is getting 8 (!) different regiments, with Stratagems, doctrines and special orders.
I think GW is going "simple rules - lots of options" way for 8th edition, so i think every army will have at least half a dozen sub-factions to chose from, and often more.

Re: the datasheet example before.

I think this would be a good way for GW to go, as it means they can release new stuff whenever they want to without having to release an amended codex for it to be playable. Have each box contain rules for the unit/s that it contains.

Hope Broken Sigil will make it in. Thankfully fluff depicting them is terribly simple and can be used as a basis for rules easily.