Counter Arguments Towards Vaati
Why should Vaati be in before the likes of Ghirahim or Zant?
Vaati should be in before them as he has not been a one-time only villian, like the above have been. Vaati has appeared in 3 games being the major villian in Minish Cap and Four Swords and 2nd only to Ganon in Four Swords Adventures. He also still has a good amount of popularity left in him, being the 2nd most wanted Zelda character.
Vaati hasn't appeared in a long time, he shouldn't be in the next Smash!
Neither has K.Rool or Marth in Melee. Also so you know, Marth isn't considered the mascot of FE in Japan either. Megaman also hasn't appeared in a long time yet, he has made it into SSB4, so being recent doesn't mean much. Even if you argue against them, Vaati has been in Minish Caps anniversary edition and Four Swords 3DS ambassador.
He's most likely won't ever be seen again!
Vaati actually has a large chance of reappearing again thanks to his large timeline influence, and being known by Ganondorf. Also, every time the 4-Sword is pulled out, this releases Vaati, so he could very well appear again.
In the official time-line there is a big gap between 4-swords and 4-swords adventures which means he could reappear in that timeline again. He also could appear in the other 2 timelines, as he was not defeated in those timelines yet, which leads me to believe that Vaati could be in Zelda U, which may be multiplayer, and Vaati fits a very good role for that game, especially if they use 4 Link's again. He could also be in Hyrule Warriors as his artstyle seems like it would fit pretty well in the game and he could be used as a boss in it too, probably even the final boss if Ganondorf doesn't appear in it.
He has never fought in his normal form!
We may have never seen Vaati fight in his normal form, but he shows that he can when he teleports and pushes opponents away with his magic. Most of his moves in his other forms can also be easily incorporated into his human form and it wouldn't look awkward, especially most of his moves from the Vaati reborn form, which looks almost just like his normal form, only taller and more features on him.
Impa and Tingle would be better character than Vaati!
These 2 characters are probably the biggest threat to Vaati, however Impa hasn't appeared as an actual person who could fight very often and wasn't that important in very many either besides from her usual starting you on your quest. The only games where she could actually pull some important potential is in OoT, which Sheik was actually a bigger character in, and Skyward Sword which is probably the only version of Impa that is actually important to the story as a whole and could actually fight, at least in her younger form.
Now compare this with Vaati. In all of the games Vaati has been in, he was very important. He was either the main villian or the secondary villian only to Ganon himself. Vaati's importance was also in 3 games, unlike Impa who was only majorly important in one and was overshadowed by Sheik in the other, while not having very important roles in the other few Zelda games she's been in. Impa would also probably fight alot like Sheik but Vaati is almost impossible to make a clone.
Tingle doesn't have too much importance to the Legend of Zelda and about half of his appearances are as cameos. In the games he is important in he either only sells you maps or fuse kinstones. Tingle makes most of his importance in his spin-off games and if we were to count those, than Tingle would be counted as a spin-off character than an actual Zelda character.
Nintendo doesn't seem to like him, as his games were also co-created with Capcom.
If Nintendo didn't like Vaati, wouldn't it seem weird that they used Minish Cap as a 3DS ambassador and gave 4-Swords an anniversary edition? Also, Four Swords Adventures wasn't made by Capcom, yet Vaati was in it.
Vaati's games aren't well liked and weren't very advertized!
Vaati's games are actually well liked by the public, being very highly acclaimed. Four Swords Adventures was ranked the 48th best game ever made on a Nintendo system by Nintendo power and received an 86 out of 100 from Metacritic. It was also the 3rd best selling game of June 2004 in North America, with 155,000 units and has since sold 250,000 copies and sold 127,000 units in Japan. Minish Cap was also very highly acclaimed. It was named the 20th best GBA game in an IGN feature, and was selected as the 2005 GBA game of the year by Gamespot.