Though I've stated a preference for post-Klondike Clans, I quite like the Chaos March idea.
Considering the size of the area given, it makes each planet that much more valuable. Especially with resources. And with several factions already given, it has a nice starting point while at the same time allowing for personal innovation. A player can create a whole new faction, or take an existing one and invent nearly every aspect. Though having already established factions is appealing in a different way, this one can encourage creativity.
With the military forces of a faction in any game rarely established in canon (notable exception: Field Manual series), it can be hard to balance factions (or unbalance them, if so desired) without bickering. Hopefully, a smaller area can be easier for GMs to distribute military force. In addition, it gives more face time to individual units or single heroes, making each unit's story that much more memorable. At the same time, it eliminates some problems. No WarShips, for example, or some problems with massed forces.
In particular, I was struck by the players as mercenary idea in the Chaos March. Usually, there are a number of players wanting just to be mercenaries, not nations. This solves it quite nicely, both in established units (e.g., "I want to be Wolf's Dragoons!") and player-created units ("I want to make my own!"). In a large game, a sudden appearance of a multi-regimental non canon mercenary unit can be unwelcome, but in a smaller game, a lance-sized unit would be believable. However, the best part (in my humble opinion) is the personal control. In the large strategy games, mercenary players are often beholden to their employer with little chance of creative input but service. In a smaller environment, with factions less able to control mercenaries and less powerful to stop mercenaries, a private company could do much more. They could suddenly switch factions and cause change much more significant in impact than a larger strategy game. They could form their own faction suddenly! They could charge exorbitant fees in the mercenary-heavy worlds. Or perhaps they might be crushed and forced to rely on the good graces on a faction. Many options, quite variable.
Lastly, the existence of the Successor States nearby can create readily-made GM events. For example, a Lyran unit may go rogue, or the Suns is looking for a criminal placed within the military of a Chaos March faction. Though this would preferably not be used too often, it gives the GMs a good start. Though I liked the neutral ComStar GM faction of the 3010 game, this one excites me more.