The lack of forward-delete (and arrow keys and PageUp/Down keys) is disastrous, and very nearly halted my transition from business Windows laptops to iOS iPads. The Apple Store Genius explained that apart from no mouse facility, the iOS developers deliberately exclude fwd-del from the key mapping - it is simply not programmable for Apple products or third party products.
However to my astonishment, my new iPad Pro 12.9" 256gb on iOS 10.2 pairs up with a bluetooth Wireless Apple Keyboard model A1314 bought in 2012, and fn+ <— works!
Yes, function-plus-backspace actually deletes forwards!! Yippee!
Two Further Points of Interest:
1. Bluetooth pairing is a pain. Today I realised that when making the keyboard's green light flash by putting it into Pairing Mode, you must keep your finger pressed on the keyboard's battery button while asking the iPad to pair. Only when you're given a code to type in may you release the keyboard button....
2. In th Store we tried connecting the new wired USB2 "Apple Keyboard with Numeric Keypad" to the iPad Pro via a 'Camera Connection Kit'. The iPad's power manager refused to supply power to the keyboard and so would not connect. Perhaps supplying USB power to the CCKit would have helped - the Apple staff were not prepared to try it out, and again argued that iOS is not designed to support the keyboard map of the extended wired keyboard. It might have worked today, but it is an unsupported feature and so might not work after tomorrow's overnight iOS update...
George