Yep, goto: http://battlefieldsingleplayer.planetbattlefield.gamespy.com/ I've been runnig 32 & 64 player Coop maps for sometime now. Takes a bit of work, but well worth it.
Err, well, that's sorta delayed... Life got in the way. ( All I can say at this stage is, I'm close. Some last minute bugs have apeared that I need to sort out, but other than that...
There might be a new version of the client aswell, cant tell for shure yet though, but maybe.... If everything goes right, it will get around the hosts file check Dice implemented...