I recognize the benefits of having multiple races and homelands in one guild- giving players the opportunity to specialize in one area will both help the group strategically and let individuals develop their own tactics. Therefore, I will accept all races into this organization.
The way Dominion has the advantage in war is by having members of all different races use their strengths to fill the weaknesses of others, which in turn allows members to focus on specific types of units without sacrificing an overall diversity. By having a human player focus on cavalry and anti-cavalry units, an Orc player focus on mass fodder units and siege, and an Elven player focusing on long range and elite melee units, every base is covered and players can use their units to the greatest effect, because they don't have to worry about micromanaging multiple types of units.
I was thinking along the same lines as you. As long as Orcs have some geared, tech'd, and experienced fodder, they can play with other races and compliment their armies, no matter what that ally has.