custom keyboards

I develop Typefinity, a custom keyboard app for iPad and iPhone designed for usability and efficiency on tablets and modern large phones. • Number row and full punctuation on main layout • Cursor keys • Opt key to access additional symbols and accent keys, and activate move / delete by word...

I’ve been looking everywhere for a Keyboard that will let me rearrange/Replace original keys with Custom symbols or Glyphs (e.g Switch the letter I with say ! Etc.) Anyone have any ideas?

I noticed that on the Apple HIG, it says that custom keyboards should not implement emoji or dictation buttons because they are shown below custom and default keyboards. This is amazing news since native dictation was always a sorely missed feature with custom keyboards...