Personally I think too many classes get full martial proficiency, martial weapons would be so much more meaningful if classes that got any martial weapons only got say, four appropriate ones, then the few you did get would be more significant, (and a boon to the fighter being the only one to get full access)
Armour classification needs more nuance too but I don’t know what I’d do with that, maybe you could have a max ‘equip weight capacity’ between weapons, armour and shield so unless you’d maxed your strength score you’d have to compromise between the heaviest good armour (in your equipable category) and a light weapon (or vice-versa) or having both a medium weight armour and weapon
Edit: so suppose it works like your max weight capacity is 5+str, simple weapons range from 1-3 weight, martial 3-5, then armour is 1-5 for light, 2-6 for med and 3-7 for heavy, shields are 2