My two cents
Now this is a great idea, although I'd like to have a few more games under my belt before undertaking something of that scale. But, for the sake of playing devil's advocate here, I've got some suggestions for you, if you're serious about trying to get something of this magnitude going.
First, as many other posters have mentioned, it would require that you have some sort of standard to be met in order to weed out the "serious" players from the "non-serious" players. This would not only ensure that you've got dedicated players, but also the organizers wouldn't have to worry as much about injuries and the safety of those involved. This could be a two-tiered requirement of say, atleast 3 games already played, and confirmed by the organizer of said games, as well as a standard of gear required. By standard of gear, Im thinking: Must have a radio (for organizational ease), full kit (Including camo, vest, gun, goggles...blah, blah...) as well as the appropriate camping arrangements.
Second, I think you would benefit from having a team of organizers, so that you don't have to take the full brunt of organizing everything yourself. Perhaps other experienced vets in your area could help out, get some planning done. As a side note, you could appoint two of these people to be "team leaders", or whatever you'd like to call them, which would be responsible for helping enforce rules, scenarios, etc... while in the field. This would also help you organize the entire scenerio better.
I like the idea of not having safe zones, as it adds an aspect of realism to the game. As a possible answer to the concerns over always having goggles on, perhaps you could enforce a rule that inside tents, etc, you can take goggles off. To add to that, you might want to think about enforcing a rule that if someone storms into a tent, those people are "hit" so theres no point blank firing going on against people with no goggles on. Just a thought, but it would need more ironing out.
As for the layout of the scenario, it could be something similar to a "take and hold". By this I mean the objectives of both sides is to infiltrate the enemy encampment, seize control of it, and hold it for X hours. This could be done by assigning a "base command" building/area, which is what would need to be held for the X hours.
If I think of anything else, I'll post it up, but I think you should take some of these things into consideration.
I knew a man once who said "Death smiles at us all. All a man can do is smile back."