You can use created players in MM, they will be free agents or whatever you call them.
I really like how they did the career mode with player, manager or playing manager... it's perfect and something that I have been asking for in their feedback section, thank you EA. By putting in playing manager I will finally be able to play that mode.
The talk about AI sounds great, however it could just be a load of bollocks. I only play offline so if they can actually make the AI play much more realistic and different every game it would make the game so much better.
One thing that I've forgotten to leave feedback on (I think) is that when playing BAP you should not be able to make team mates pass to you. You should only be able to "suggest" that they pass to you (like in PES), currently they always pass you which is very unrealistic. Also you should not be able to make them shoot. It is supposed to be a mode where you only control one player, but they've added those things that ruins the experience imo.
Also being a captain should not make you the manager. At least there should be an option to turn it off.