I have tried to convert the DB (I wanted to use it for friendlies with friends as we still prefer FIFA12 too), but it lacks a lot of names and stuff...
I also don't know how it will behave during a career as I'm not planning to play a career with it and I've not tested it.
But if you're interested in the players/promoted teams/transfers, it has all of them as it features the real tables of FIFA14 extracted from the game and converted to the FIFA12 format:
Of course it has a lot of flaws at the moment (many players have no boots, many have no face or hair, some teams have green and blue checkered kits because it "looks" for graphic files that just are not there) but it has the right squads, numbers, promoted/relegated teams, and the new leagues (even if many teams show no name ingame at the moment, I need to investigate it further).
Also, I cannot say what will be the impact of it to the gameplay as FIFA14 doesn't feature the tacticalawareness
fields that are present in FIFA12.
I've added the correct values for the players that had those values in FIFA12, I set them to 50 and 50 for the ones that hadn't.
So, if you want to try it, just remember that it's experimental and provided "as is"!
Also, feel free to modify/update it as you wish.