Have MF's ult scale Better with Actual ADC Items than Lethality/Armor Pen

The way to do this of course would be to lower the base damage or AD ratio slightly, but then boost the amount of bonus damage it does when critting.

The problem with this is that it would make her ult damage more unreliable (which is not good for either MF and her team or the enemy team). So it shouldn't be a massive change. But I think Riot had the right idea when they reworked her a while back and gave her the bonus 20% damage on her ult when it crits.