Why is Tristana getting a skin vote?
The reasoning for Illaoi was that she is unpopular and requires a lot of work for a skin, so Riot wanted to make sure the one skin she might ever see was one that would be popular. But Tristana is a popular champion with nothing especially difficult for skin production and gets skins all the time. If all three of these skins are good ideas then it's not unlikely for her to get all 3 skins within the next few years, so why the vote this time?