I foresee a couple of problems with this plan - firstly, you've equipped the model with a halberd, which according to the rulebook counts as an axe. WYSIWYG players might pull you up on this (I wouldn't, but some might, and you would have to make sure your opponent knows what you're intending it to be.) Secondly, the benefits of the power maul are outweighed by the drawbacks. The AP 4 makes it very unhelpful against MEQ, and if you gave your Archon combat drugs he might have plus one strength anyway (plus two with a second pain token). The concussive part is nice as a feature, but next to useless for a character that's initiative seven already - it'll only really be useful against high initiative special characters, ie Eldar phoenix lords, and he won't get through their armour anyway. Any armour that he can cleave through he wants to be inflicting instant death with the hits, making the huskblade the better option (in my opinion). An agoniser is probably better than the maul really, as it lets you ignore more armour saves, and wound bigger stuff.
My other car is a Ravager