ooh now that's a stable looking pile of iron. Shame about it's teeny little gun. You'd think it would have room for a heavier weapon. There must be something very important in that large structure on the top. From it's aircraft tower like shape I'd wager these mechs coordinate the other mechs.
Depending on size, seems like it would it serve as a mobile forward operating base. lower guns covering for infantry, maybe armor piercing rounds. Upper guns are for anti air/long range artillery bombardment.
Possibly artillery; the size and sturdiness of the legs would support a massive amount of recoil, and it doesn't look fast enough to be a frontline combat unit. Alternately it could be a multipurpose mech, with a hardpoint on top for mission-specific turrets such as anti-aircraft or missile battery.