I understans fire's concerns about EU continuity, but honestly, I seriously doubt anything is going to come along and invalidate anything we do in the campaign. We have chosen a very specific time frame for the game and with the Zahn books looming in our timeline (whether we start the game with Thrawn or not), the likelihood of someone picking that exact time (and part of the galaxy) to start a trilogy seems unlikely.
"the odds... are approximately three thousand, seven hundred and twenty to one!"

I hope you know you've basically *told* Lucasfilm to do this very thing, eh? ((throws salt over shoulder, turns three times and spits))
Okay, fine by me, then. We can even be *after* the Thrawn series, and I'll just run a game with this in mind.
But we'll need a way to transport Jedi from Yavin to the sector. The premise can be that the Alliance always wants some Jedi to be stationed in this boarder system to the Empire, and be on the lookout for trouble. Anywhere the Force leads them after that is fine, keeping that in mind.
Also, we should increase the numbers of Jedi who've been training at Yavin. We'll maybe have piles of PC jedi, still not many by Galactic standards of population, but it would make sense.
We should be creative with the Haon system, and En, for sure. It's a setting, it needs a baseline of people in it that serve as setting important-people.
1) Hive of scum and villainy: we need crooks to hang out here, and space traders, smugglers, etc. Makes sense for a system with traffic like Haon.
2) Alliance Embassy: I vote for House Organa. It's an organization detailed in Force Unleashed, and allows for plots involving Leia and others. In theory set on En where all the aforementioned refugees-turned-citizens live (I really like that idea, too).
3) Planets in the system and what they're like. We could leave this vague and have a pile of planets and moons for GMs to work with (like Firefly had). Haon could be a great place to disappear with so many options.
Or not: we could have several specific planets, each with a particular purpose. The rest of the galaxy the GMs can add their own environments, obviously, which is simple to not worry about.
4) I'd really like to have a Jedi outpost, if not a temple. If people want to be all Jedi-emo, they'll enjoy having a place to hangout other than Yavin.