I remember suggesting "mech classes" once on Kongregate.
idea is that, aside of Normal mech (2 actions per turn, 1000 weight), player can assign his/her mech as Heavy or Light.
Heavy mech have greater weight limit (like 1100-1250), +15% hp bonus and +4 to all resists. However, this mech only have 1.5 actions per turn, skipping one action each second turn (skipping, not just shutting down - this means that mech can be prevented from even firing a drone by merely normal overheat, not double one)
On the other hand, Light mech have advantage of gaining +1 extra action each second turn (2,5 actions per turn total) or may be even each turn (3 apt) - at cost of having weight limit reduced to 800-900, 10% hp penalty, -3 all resists
All classes should be mutually balanced and thus allowed to be at same matchmaking in arena. Balancing their usage in single player is low priority.
I totally know this will be hard as hell to balance, but imo base idea (gaining extra weight capacity in exchange for battle speed and vice versa) is good. And it sure can add even more creativity for mech building