Eh you'd be surprised. An Open Source solution created by the fans could probably be better than FFG's one, assuming there's interest. There's probably more programmer fans that would work on it for free than FFG has employees working on it. Doubt it will happen, but I've seen it happen in other settings...
I agree. There are a lot of programmers out there who love board games and play mansions. It would be great if FFG released an official editor but if they are misguided enough not to do so, I would be surprised if an open source solution was not created. FFG could not do much about it as long as the solution did not use images from the game.