I definitely think the durability system would be extremely interesting, with many more features which could be tacked on,
e.g. repairing armor, makeshift armor, crafting, sliding in armored plates and stuff, armor mods...
And it'll also make fights more dynamic - you could possibly win through attrition in prolonged gunfights, instead of trying to cheese it by injecting sleepy juice and slicing their head off.
Also, cross resistance damage. Taking a bullet in your radiation suit means radiation will leak in - leading to both reduced bullet and radiation resistance.
However, it'll also make it exponentially harder and a P.I.T.A to code as well as balance properly, since you know, there's so many variables.
Unless you're up to it, of course, which means just no problem.