While many gamers may feel that "marines are marines are marines," there's actually quite a lot of variety between the different chapters. Each has access to different vehicles, wargear, and psychic powers. Even various unit structures can be different between them. As such, while they're all running around in the same style of armor (generally speaking), one chapter can play a lot different from another. One Page Rules is bringing those differences to their One Page 40k rules set.
With that being said, the main rulebook now has Blood Angels and Space Wolves in it. They've also put the Dark Angels chapter back in, removing it from the Fan Armybook. Go see how you can play your forces with this new update.