Vayne is a good model for Riot's new champ but...
There are some things I hope Riot doesn't give the new ADC. Here's how I'm seeing things
I see Vayne and Draven with equal skill curves.
Jhin requires more game knowledge than mechanics.
Between Draven and Vayne, I wouldn't mind either as the model because they're the only mechanically intensive ADCs out there. Every other is pretty easy to get down and takes much less mechanical strength. I believe Draven is harder to base off of for a void-based ADC IMO though due to how unique it is.
(Hoping for a Draven rune though - hopefully)
Anyways, if Riot is looking at Vayne it's a good thing. Because other than Draven, she's the only mechanically intensive champion with high risk/reward that doesn't offer some untargetability, period of invulnerability, or insane damage. She's also much less annoying than ADCs like:

Granted that Patch 8.1 Vayne was hell due to everyone else getting nerfed and her kit requiring no skill. (Great nerfs BTW Rito)
Draven's kit itself is a lot more unique than Vayne's as well.
I just hope the new ADC doesn't have:
- Stealth
- Offer some invulnerability/untargetability (Yasuo windwall, Camille ult, Kalista ult)
- Poorly balanced damage (Zoe Q)
- Is not as boring as Kog'maw (W W W W W W W W W W W W W Q R W W W W E W W W W W PASSIVE)
I believe the mobility of Vayne's kit and the damage trade off from Draven's kit are amazing examples of balanced, high-level mechanics for ADCs.