Yes pros and others sometimes mock built-in pop-up flashes and always use full size shoe-mounted flashes. However sometimes, especially when traveling or on vacation, you find yourself needing a flash, and you did not bring your big flash with you. Also, the pop-up flash is great as a fill light. Given todays ever more light sensitive sensors a small, light, low power flash makes more sense than ever!
The GPS tethering via bluetooth is a nice solution, however it is sometimes difficult to connect. It would be better if the camera always reached out to the phone, and it should not be necessary to manually open the app on the phone.
Build a grip that holds two batteries, but also allows a battery in the body (same as Fuji X-T2 grip functionality)