I'm not the GM, but wouldnt a mech that could counter everything kinda break rule 1? And wouldnt that also break the need for frame categories? Why name it a heavy frame if it can keep up with a lighter frame?

These are just my 2 cents, coming from someone who adores the Battletech universe, but classes keep things balanced. Heavier frames might be able to carry more weapons and armor, but they're countered by lighter frames that can dance around them, which is why you'd want a well balanced team that can handle multiple types of threats.