Here is my guildies' idea:
When team starts GvG, they leave with 9 players. 9th player is a backup. At the beginning, he is in "dead party memeber" mode, the difference is that he can only switch between NPCs in your base, he isnt visible in party window. When someone is accidentally disconnected from a game, 9th player comes into a game. He controlls disconnected player's character.
ATM i dont have any idea if he should be spawned at the base, or continue play of dc player. He keeps DP and all other stuff.
After battle he comes back to his origin character. This could solve problem of loosing GvG because of disconnect..
Hope it wasn't posted before...
Sry my english
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Starting at the base, or in the largest group of your teammates, would probably work best, but I don't GvG alot, so I don't really know.