You wouldnt really need that many players for a war to look massive in a 3d game. I mean if you had about a 100 people in one area 50 on each team. It would seem like a massive army with all the chaos of players charging each other and I tell you when you're fighting 50 other players in 3d it's crazy especially when you cant see who is at your back and praying to god that one of your own guild members is behind you and not a rogue from the other team getting ready to back stab you. ;x Last time that happened I ran with 3 guys after me and I got lost and died. ;x My whole point is you dont need thousands for it to be exciting.
With even 20 on each team it would be equally thrilling.