I like Shalira idea, but how do you justify that Khanid strenghten their autonomy while the last years have proved exactly the opposite ? Now Khanid II is once again part of the privy council (even as advisor only). That would require some sort of important event to backpedal like this.
Now then, I do think that one can find casus belli between all the factions, whatever you may think of. It is not really hard, they all have their grudges against the other ones. Yes, even the Gallente vs the Minmatar. Like the Amarr / Caldari, they do not share a lot of things (unlike what people always tend to think). Not that a free for all would be a good solution though, but the whole thing gets more granular and offers more possibilities. Especially when you start to add new minor factions in the equation, like for example the Ammatar Mandate, which can be a key actor where with it alone, you might be able to put at war 3 of the 4 empires : the Amarr vs the Republic because its obvious, but also the Caldari vs the Minmatar for business opportunities (as stated in the chronicles).
Besides this, I think like Senn that people tend to overestimate the implication and patriotism of the average dude, whatever faction he is living in. Sure you will always find activists here and there, but seriously, why even the usual Minmatar worker would care about his so called "brothers" that have been enslaved for centuries, that he has never seen in his life, and with whom he does not even share something (except blood ?). Because of a national feeling ? Propaganda ? Sure. Like IRL when the media start to talk about Islam or China all the day, saying "booooo". But does that make the average citizen willing to go to war with them ? Not really. They do not care. People usually care about themselves first, thats human, and after, they extend that to their families, whatever their culture is. But the people actually "going activist" are minorities compared to the "masses". I am no fool, it is quite obvious for me that why factions, even in Eve, are fighting each other, is for pure political agendas, even the Amarr and the Minmatar. Not for the ideological sugarcoat. Not anymore at least.