They already said they were bringing Krile to Dawntrail since she is a more underutilized member of the cast. The other Scions were off doing the cool stuff or got to go to other worlds while she ended up getting left behind doing stuff like getting kidnapped or getting possessed.

They could have just made up a new character to be the main Pictomancer, but they seemed to be intent on bringing Krile into the main picture and I don't exactly see her as Viper. Also not sure that you can say it can't suit her considering she has the most cutesy/cartoony outfit in the entire game among the main cast and has a hood with cat ears on it.