WWWWWOOOOOOOOAAAAAAUUUUUUUUUUU!
what a long please
Is not so hard to do it yourself
0)make a backup of cm12.1 rom
1) install via ODIN any stok version(the last one is good) without unroot or other stuff(this work without unroot)
2) install via ODIN TWRP_3.0.0.0 it should work without root(if doesnt work without root, then root the phone and follow the procedure)
3) make a backup of stok rom with all your personal setting and then save it on the pc (will be huge 2>3>X Gb)
4) wipe advanced dalvik/data/cache/system/ and-sec
5) restore cm12.1 backup and enjoy it!
Now when you want a stok rom
just copy the backup in TWRP backup folder
and restore it and will be no need to set it every time you use it
If you have a big space on the sdcard you can keep the backup on it
just rename it to "Stok_backup" or something else