I suppose that's the thing. The Empire has by far the best gunline in the game, it's just a matter of protecting it from the hordes of Miners, Tunnellers, Chameleon Skinks, Terradons, FSOD's, Striggoi Vampires, Wyverns, Dragons, Shades, Pegasus Knights and the misfire dice.
Basically, any army that packs a lot of hard infantry to keep the enemy away from the Empire artillery will be a good playing partner.