Mech weight forces you to think carefully about what you choose to equip on your mech. Without it, players could just equip all their strongest items on to one mech with little thought. Right now you have to think about what you're going to sacrifice (whether it be top weapons, a few side weapons, no shield..) to get your mech to work.

In the future though, there is a possibility of a 1200kg weight limit which will allow you to add more to your mech

High weight on strong weapons is as good of a way to balance it as anything else, simply because it's "not enough", and it's not supposed to be enough either. I might agree that there is an argument to be made about it being "to much" weight for lower levels, meaning it is less strategic, but what soulution is there for a good way to slowly increase the weight?

You wouldn't be able to hit 2000, no matter what combination you used. Might as well have no weight at all