The issue with modding a fixed nutrient is you only have a limited amount of elbow room. If you add something, you have to take something away to maintain the EC. With a fixed nute, you cant remove say half the N without taking half of the P,K,Mg Fe etc along with it. Now your N is golden but something else is too light

By the time your done making the preverbial square peg fit the round hole it`d be easier and likely cheaper to make the nute up from scratch