Giving Vayne Counterplay

So, Vayne's % Max HP true damage is a problem. There is no way to build against it (especially since she has autoattack resets, so AS slows aren't super effective). I propose a solution:

Recode Vayne's Silver Bolts as physical damage that penetrates 100% of armour. Or as magic damage that penetrates 100% of MR. I don't much care, though she can get some heal from physical damage she can't get from magic damage or true damage, so I'd prefer it be magic damage. But why is this a good change?

True damage cannot be reduced in any way unless the unit is invincible. Magic and physical damage, however, are reduced by other effects than armour and MR: Exhaust: 40% Urgot's passive: 15% Sona's W Power Chord: 20% Alistar, Braum, Garen and a few others also have abilities which reduce non-true damage by a percent. So the effect of the change would be that it still penetrates but there are a few situational effects which allow some counterplay.

Note that Exhaust can, in some situations, do almost nothing to Vayne's damage output: Auto-tumble-auto-condemn is still fast and procs Silver Bolts.

Short of doing this, it would be really nice if Exhaust reduced Silver Bolts' damage as an exception to the general rule, so there's at least something that I can do against Vayne.