Unfortunately Ubi Devs have already said that there are no plans to do 6v6 or 8v8, even in Custom matches. They said they tried it during the initial testing of the game and it just ended up turning the game into something they were not interested in. I guess its something that they could revisit later on down the road but at least for the foreseeable future, the game is gonna stay at 4v4.
On a bright side, they have said that they are going to be making a hardcore mode for Custom games, where there will be no HUD or mini map or marking, but itll only be for Custom Games. So hopefully that helps.