I have yet to attend a game out of province, although having run a large public op I have an idea on what kind of planning and forethought has to go into a major event whose scale can accommodate a large number of players.
This type of event is completely feasible. The only thing you need to do is find something that makes it worth the flight/drive for the majority of players that will be attending from outside the locale. To me, that's the most difficult hurdle.
Because we're a hobby-based sport with no real sponsors or capital aside from what we spend ourselves, getting enough scratch up to build a worthwhile scenario is outside the means of most of us. For my team's first game, Operation: Prairie Wind, we paid for everything out of our own pockets months before the game. We only recouped what we spent AFTER everyone had shown up and paid their entrance fee. In order to build a massive scenario complete with suitable land, structures, props, vehicles which would be necessary to make it worthwhile, you would need to be fronting a lot of cash that you really have no guarantee you'll ever see back again. One way to minimize your loss is to have an advance signup with an incentive for pre-payment, but you'll only get so many people doing that because they're buying into an unknown.
Location is important, but make the game interesting or cool enough and it will become a moot issue.
My biggest desire right now is to be able to play in a game that has developed structures, or at least ones that make an attempt to appear as such. Watching the Op: Irene videos gives me a hard on for all the multi-storey buildings, paved streets, and courtyards you can fight in and around. I realize such a grand facility is impractical here though all of the outdoor games I've played thus far have been strictly woodlands based. You start to yearn for more.
Where can we go that has enough varied terrain to be interesting, developed roads so that vehicles of any sort can be effectively employed, but is remote enough so as not to interfere with the public, can have structures built upon it either as semi-permanent or permanent, and can be terraformed to our liking?