I get really irritated when people go AFK during my turn and dont select casualties. I think there should be a timer that automatically selects casualties for them after a set duration has past (60 seconds sounds about right). The game already autosuggests casualties so I dont think it would be too hard to implement.
I would suggest allowing it to toggle on and off during the game, much like sound. Biggest problem with autoselect is it kills bombers before inf.
Another way to speed up the game would be to have an auto dice rolling as an option for a particular battle instead of requiring you to hit space each time. Most helpful in battle such as 2 inf attacking 1 inf or a sub vs a transport.