Something that always seemed a little weird to me with the advent of advanced armors is they don't really do anything to directly change the maximum amount of coverage available to a certain section. While lightening the burden does allow for more armor to be installed, it only helps if you haven't already maxed it out. Changing out an Atlas' or Dire Wolf's armor to Ferro-Fibrous won't really change the values it has, it just reduces how much the armor weighs, or sometimes what.
Now sometimes more advanced armor will change how the damage is taken, such as Hardened Armor, but that's not exactly the same thing I'm talking about here.
Now, I'm not saying I've figured out how to do this, but what if each limb or section had a set amount of weight of armor could be carried instead of a certain number of hit points that it carried? For example, a 100 ton mech's frame will allow for 2 tons of armor to be carried on its arms, while the 75 ton Orion can carry a 1 1/2 tons of armor, just to start off the brainstorming.
Of course, this doesn't allow for the fine differences between the maximum armor that a Orion's chassis and a Zeus' chassis currently can carry, and I think that fine distinction is why the current system was set up and hasn't really changed.
The current build system is a little backwards starting with end mass first and working upward from there, but then, there is no downside to having all Mechs of a class use the same skeleton mass, but underbuilding it, such as having a Locust and a Panther having the same skeleton, but under-armoring and under-gunning the Locust to keep it at 20 tons vs over-armoring and over-gunning the Panther's 35 tons. Obviously speed would be another factor, but it's not like drop weight is anything but a self-imposed limit.
Apologies if I seem to be rambling, but what changes in armor distribution do you think would be good for the game?