Alright, let's start this shit. I'll start with a rough concept and post it in a week when I've finished and everyone has forgotten about it entirely.
You got 5 attributes, alright? Goes Fast, Toughness, Accelerate, Handle, and Maneuver. You are also provided with 30 points to buy these attributes.
Armor: How much plating your machine has.
Toughness: the internal integrity of your machine, used for preventing crits
Accelerate: Amount that speed increases per turn.
Goes Fast: Top speed and likelihood of losing speed if hit.
Handle: How well your machine corners and holds its shit together when it's missing two wheels.
Maneuver: How well your machine can jump, cross terrain, etcetera.
Now armor comes in two types: External, and Internal. External armor is determined by your Armor, and the total number of AP is equal to your armor x3. You then distribute your armor between your top, back, front, and sides. It's important to figure out your machine's weakpoints, because having uber-armor doesn't mean shit if the enemy can get at your soft, turtle-like undercarriage. Your internal armor is special, because you can only hit it on a side with no armor left, and if it's hit, you have to roll (toughness) - (the number of times your armor has been hit previously) to avoid having your shit explode.
Movement is mostly governed by Fast and Acceleration. Your top speed is Fast x3 inches per round, and your speed increases by your acceleration each round, though if you really need to(and trust me, you often will), you can redline your machine, doubling your acceleration and raising your top speed by 1 multiplier(IE x3 to x4) for the round but halving your handling and requiring a toughness save to keep from blowing up your engine.