Why not turning it to a box match?
There might be different rank and tournaments for, for example
600= feather weight
800=light weight
1000=Medium weight
1100=Heavy weight
1100+=Super heavy weight
Even, there might be different weight limits for different battles on campaign mode. In every campaignn mode game, the game might put another weight limit and the robots you face would also have that limit.
We would need to arrange our tank to these different limits, or we might just not havve any limit

This would add to thhe game more "target" to reach and solve whole weight discusses.

Thanks..