I know they're heavy I hope I can get it to work. Saw a pair for£30 and couldn't resist!
But I have some drill motors handy too if needed.

Rough calculations:
Drives x2 = 4kg (I think the ones I found weigh 1.9kg each)
6S LiPo = 1kg (depending on size - I estimate 4000mAh should suffice but have budgeted for larger)
Wheels = 1kg (these are heavy tough ones quite wide, could save weight here)
Brushless motor = 0.31kg (Turnigy XK series inrunner)
RX & ESC x2 = 0.2kg (Turnigy/FLYSKY RX, FeatherTwo, Hobbyking 80A)
Armour/chassis = 6kg
Bearings, weapon disc and misc. = 1kg

I'd like a self right mechanism in there too but perhaps that would push it over the limit.
It's a bit of an experiment, and may need adapted. If it's anything like Evil L'Weevil it'll be a under my estimates. EKW came in a full 100g less than my calculations.

Once the motors arrive, I'll weight them, finalise the dimensions of the chassis and update my calculations. The wedge slope needs to be a low enough angle (35' would be good). I am concerned I have over cooked it, worst case I use this pair of motors for an axe weapon system on another concept I have.