Dedicated servers to prevent the current lag issue or search options where you can search for good connection and if your connection drops below a certain level you get kicked from the game to stop your poor connection impacting others!
An option to lobby with friends before you search for a game online in order to let you both join the same game rather than looking for seperate games and trying to join one with a space in before it gets filled.
The fact that turrets cant be repaired until they are "downed" if they get slightly damaged you should be able to repair them and it should also highlight friendly turrets in the area as an engineer so you can repair them also.
Engineers can remove hack boxes far too quickly it should take roughly the same time to remove the hack box as what it does to hack with the hack boxes.
Just wondered what you all thought of that especially the developers and please feel free to add any more ideas