Curious about how well having that C++ core to share code has worked out for you in the past. Apart from low-level contained code that doesn't require access to too many OS interfaces (user I/O, network, threading, GPS etc) I can't imagine it would be easy or useful to have a C++ core.
Usually C++ runs core logic that cannot go on the server (that's things like your own custom client-side crypto, parsing, or other "pure computation") and then you make the user interface in Swift or Java depending on your platform.
