However I disagree with the starters here.
Piplup should be kept for an eventual Legends Zygarde in Kalos. I was thinking Froakie instead.
Treecko is fine.
Fennekin is fine, especially with the mystical fox theme, but you can't really have her if you already have Froakie from gen 6, so I'd say either swap it with Litten, or swap Froakie for Sobble.
That way you keep a strong ninja theme.
Of course, all of them would have regional final evolutions, so you wouldn't get abominations like Incineroar, Inteleon, and Delphox.
The plot would be time travel again, but it's kind of required with Celebi.
