Planning on keeping it fairly basic, d20 modified by pilot and robot stats, then straight-up numbers for damage and armor.
Further thought: Since the movie focused fairly heavily on the design of the robots as well as the abilities of the pilots, I would be open to adding R&D elements between bouts (after the next battlefield is decided)
Uggh, the above is clear evidence that I shouldn't post just before going to bed, here, a much more comprehensive breakdown:
The game will be handled in phases. First will be the pre-match phase, R&D happens here, as well as any attempts at espionage. Second is the battle, this takes place in two stages, all-out combat and close combat. Finally comes the post-match stage, here the council decides the winner of the battle and each side can challenge the ruling for another round of combat.
There are three 'classes':
Jocks, who pilot the robots in combat, their attributes are handling, gunnery, specials, and systems.
Designers, who develop the robots for battle and outfit them, their attributes are motive, armor, weapons and theory.
Strategists, who direct the jocks from the ground control center and whose attributes are logic, intuition, intelligence (in the military sense) and motivation.
Character creation consists of choosing a class and distributing 10 points across the four attributes of the class, attributes have a minimum score of one and a maximum score of five.
All rolls will be handled by me and will be done with a d20, attributes ranks are treated as a plus 1 to your roll (so if you have 3 in gunnery you get a plus three on all rolls related to gunnery), and then modified by equipment and circumstance.
Espionage is handled by one side requesting an espionage roll, if successful I then choose a member of the opposing team and inform them that they are being blackmailed, it is up to the player to decide whether or not to play along, though players that admit to being blackmailed will likely be kicked from their team.
Robots:
Robot design is fairly straightforward, there are four major components to robots:
Chassis: this determines the mobility of the robot, and affects the pilots' handling rolls, it also determines how much 'spare' processing the robot has for weapons.
Armor: three varieties for three major weapons, the amount of armor you can mount depends on your chassis, a tracked chassis can carry much more armor than a biped can, but a quadraped can carry even more.
Mainframe: this determines how much additional weaponry you can use and its overall effectiveness, for reference the more complex the base movement system is the less spare process will be available, stupendously bipeds are the most 'expensive' with biped motive systems eating 50% of the mainframes' process.
Alternative modes: just what it says, these three hundred foot tall machines can also be transformers, with two or more alternate forms of mobility available to them i.e. flight for high mobility, trcks for weapon stability, etc.
After determining the 'base' robot attributes weapons and specials are added. Weapons are kinetic (guns, fists, axes, etc.), explosive (missiles), and energy (lasers, ion, particle weapons, plasma cannons, microwave etc.) Specials are more diverse and tend to be very powerful tactical options, they can be anything from a super-heavy weapon of some variety to high intensity flares to blind your opponent, since these are so powerful they are the best targets of espionage attempts.