Agreed on Tira.It can be argued that Cervantes is sharing the Indian Port with Maxi. Should it be a Spanish port instead? Absolutely, but Maxi’s stages are generally brighter than this, so it seems they compromised by making the stage gloomy and stormy for Cervantes to share it.
Siegfried has as much claim to Ostrheinsburg as Nightmare does, and same goes for Tira to the Moonlit Woods. Raphael and Amy also seem associated with the woods, being the area just outside of Dumas Mansion. As Lisa pointed out, the desert is also associative with Mitsurugi, who was kept wandering through it by Edge Master to keep him away from Soul Edge (and Geralt-senpai). The rest are pretty debatable.
I think the woods could have been Siegfried since that's where he hanged out when he freed himself from Nightmare.
I don't know about Raphael and Amy. It has a resemblance to their stages in SC5 but I don't think is the same since in Libra and their stories, they have the mansion theme going for them.
Azwel is also heavily shown in the woods. That's why I said Azwel but that particular stage is debatable.
Tira is a good choice and resembles her Libra counterpart.
So, Azwel, Siegfried and Tira. Tough one!!!