I have a potentially dumb idea that I'll toss out there anyway, because it would partially address my biggest criticism and completely address one of my other complaints: perhaps you can ask the player to select some kind of background/profession in a sort of "character generation" menu, prior to being whisked away from their old life.
This would grant them an ability matching that background, which they could immediately use in the tutorial battle. Since they are some kind of chosen one anyways, it wouldn't create any sort of narrative dissonance in my opinion. They're just... a natural leader.
I don't know if this suits other story elements that are already in place, so feel free to discard this if it doesn't.
Thanks again and good luck with your project! I plan to check back in with it once things are a bit less busy on my end.