I'm so sorry for not giving you this before. I've been busy in regular life and not too involved with the arcade side of my computer since started using it as a platform for playing PC games.
At any rate, below is the AHK code I use to launch Injustice with joystick to keyboard mapping using VJOY.
Notice that I use devcon to disable the vjoy driver when not playing Injustice. This is because vjoy used to interfere with my setup for SFIV games and others. If that is the case for you as well, devcon is a utility that is part of the Windows Driver Kit 7.1 and can be extracted using Universal Extractor. There are guides online on how to do this or you can PM me and I'll send it to you if you prefer. Just run your antivirus on it before you use it, just in case. The kit came directly from the MS website but you shouldn't trust exe files shared online by other people.
Let me know if you run into problems.
#NoEnv
SendMode Input
SetWorkingDir %A_ScriptDir%
SetBatchLines -1
MouseMove, 0, 0, 0
Run, D:\Other Files\Non-Gaming Software\devcon.exe enable "HID\VJoy&Col01" "HID\VJoy&Col02"
Run, C:\Program Files (x86)\VJoy\VJoy.exe -file "D:\PC\Injustice - Gods Among Us UE\VJoy.ini"
Run, D:\Steam Games\SteamApps\common\InjusticeGodsAmongUs_UltimateEdition\DiscContentPCG\Injustice.exe
Process, WaitClose, Injustice.exe
ESC::
Process, Close, Injustice.exe
Run, C:\Program Files (x86)\VJoy\VJoy.exe -exit
Run, D:\Other Files\Non-Gaming Software\devcon.exe disable "HID\VJoy&Col01" "HID\VJoy&Col02"
ExitAPP
return