It's actually not "currently" possible for a GM to port into battlefields and nobody is going to have the time or the inclination to do that in my opinion. In fact the more I think about this, I can just see what would happen. Instead of people sending screenshots of people cheating or whatever in battlefields, I would start receiving complaints about the Monitors abusing their power and kicking somebody for the wrong reasons or whatever.
I guess we do need some GMs or somesuch, that are content to sit in game and help people, and make sure the rules are being adhered to, but it's difficult to find the kind of person that is happy to spend some of their time doing that without feeling pressure from players to spawn 10000 monsters whenever asked or to give them items or currency, or do events every 5 minutes.
I also have issues trusting people to be GM these days. Long-term players will know of the difficulties we have had in the past with GMs abusing their powers, some of which could have quite easily destroyed the game economy or even the game itself. Then again we have had some fantastic GMs, but as with everything, people get bored and move on to other things, it's not like they are getting paid for doing it, and it they don't get bored, they tire of the constant bitching and players accusing them of being a crap GM because they don't get what they want or of abusing their powers when they are doing no such thing.
Personally (and I mean that, it's my personal opinion, it doesn't mean I won't get some GMs), I don't like GMs in games, interfering with gameplay with events and whatever else. I have never really played games that have that. In fact, when I used to play retail Aion, some GMs came online around christmas time and started doing some ridiculous event spawning bosses and just handing out the best weapons in the game to random people. I was like WTF, I just spent 6 months farming to get that weapon and now this random noob just got GIVEN it for doing nothing. Maybe that's why I dislike them lol.
I guess I can start accepting applications again, but anyone considering applying should expect me to check up on them. I will be asking other players about you, and I will watch you like a hawk until I fully trust you. Everything is logged in this game - I can even see what time you farted :P