A (possibly silly) thought for Vayne...
Everyone of a certain level loves to complain about Vayne. Her damage, her W, etc. Her W at least seems to be a bit of a sticking point, at least for some people. Listening to those complaints gave me a thought that, while it may be silly, may also be somewhat interesting and POSSIBLY, dunno for sure as I'm not a designer, create some counterplay while adding a lever for tuning in one direction or the other.
When I look at Vayne....well....Blade and Batman is essentially what I see there. A brave human who hunts the night, reliant on her physical skills and gadgets to get the job done. This may be a slippery slope, but....what if she actually ran out of gadgets? More specifically....what if she ran out of Silver Bolts?
Yes, I know. Batman never seems to run out of Batarangs. But Batman is not in a a competitive game where team-play and counterplay are goals/watch-words. I can see from a direction where it seems stupid, but at the same time I also see where this provides a decision to make, and possible counter-play.
Consider this:
As soon as Vayne levels W, it is not toggled on. You have to activate it. You are given, say, ten Silver Bolts that can be refilled at the shop automatically for no cost. (her generic auto-attacks may, in theory, need to be buffed to compensate for this.) As points are sunk into W, more total Bolts can be had, meaning more seconds of that good true damage. However it's not ALWAYS on, and thus as Vayne you have to make a choice: Do you use it to burst down the tanks? Or do you use it to murder the carries faster? If they have a tank jungler and a tank support, who do you work on? How many bolts is taking down, say, a Zac going to take versus taking down a Nautilus? If you shred that tank-line, will there be enough bolts to amplify your damage to finish the carries before they finish you? Can you afford to max W first to get more bolts early in exchange for your Q and E having longer cooldowns for longer into the game?
From a balance standpoint it, in theory, may even add a lever in: Vayne's tank-shredding is too weak? We'll give her one additional bolt per level of W. She has so many that she can practically leave it on during an entire teamfight even with two to three tanks on the enemy team? Pull a few bolts off. This way LCS Big Plays can still be pulled off, and even MORE mastery can be shown off as 1v5ing isn't just a matter of solid positioning and tactical awareness, but resource management.
I dunno...probably a stupid idea, but it just occurred to me that it might be interesting to see if nothing else.