I've never actually used Ionic, so this is just my understanding from when I was looking at app-making systems.
Ionic uses PhoneGap to create the app, so all you're really doing is adding steps. Ionic has things like a base UI and AngularJS, but you probably won't actually need to use these with Twine (and it may even interfere with your story format and introduce bloat since a lot of it will be redundant). If you need any of the features from Ionic, you're likely better off just importing JavaScript libraries directly into Twine, and using PhoneGap or Cordova for the building.