First of all, how many points is he worth?
Secondly, I think you need to establish whether he's a Vehicle, a Walker, or an Infantry unit. Otherwise, you're basically making up your own core rules for a model completely unique of it's own type, which is fine, but you'll need to establish the parameters on how it's treated when in combat, or shot at, etc. For example, if he's hit by a penetrating hit, do you roll on the Vehicle Damage chart, or does he take a wound? How would Glancing Hits affect him? And would Ordnance weapons have their Ordnance effect on him? But I think most importantly, you need to establish what kind of unit he is first.
That, and determine how many points he should be worth.