You need to edit the file /User/Library/Preferences/com.apple.Preferences.plist on the device -> whether you use a jailbreak to achieve this or merely some iTunes backup editor is up to you.
Add the following boolean key as ‘true’: KeyboardEmojiEverywhere
[Update: Cydia has added this change as a package: See here for more]
Robin
razor@edgarbv.com
https://www.edgarbv.com