Not to throw a massive wet blanket on this party, but ISTR that @YXUN has been describing this potential app as something intended to be distributed on app stores. Given what I see in this thread, I think the potential for rejection is substantial, and may warrant a rather fundamental rethinking of the design and perhaps of the viability of the entire project.
Websites served in an iOS app, web content that is not formatted for iOS, and limited web interactions do not make a quality app.
– Apple App Store Guidelines, “Avoiding Common App Rejections”
Using an iframe will get you app rejected by the app store and is not recommended
– Ionic team member @mhartington