Ideas
I really hope that they will find a way to distinguish manual disconnection from internet or server issues. My solution is that if the game is interrupted in any way, next time you enter ultimate team you will be forced to complete the match from the same time, same score. The only way to avoid this should be to manually quit from the pause menu, in which case you forfeit.
To close some potential loopholes, if the disconnection follows a pause during open play, meaning not a throw in, corner or goal kick, or the goalkeeper holding the ball, it should be counted as a forfeit. This is to avoid potential cheating like disconnecting following a foul in the box, or while seeing that conceding a goal is inevitable. Every method of disconnection would cause the pause menu to be triggered, so people won't have enough time to quickly disconnect to avoid these outcomes. If the cpu has a penalty, free kick, corner, or even a throw at the time of disconnection, they will still have it upon returning to the match.
I would greatly appreciate any feedback or suggestions about what I have said, but regardless of that, all the best to you and everyone!