The champion fighter is the class you're looking for, no need to make decisions just roll to hit with every action.You could also talk to him in-between games and set up some sort of default attack action if he doesn't decide on an action in the time limit.
This is also one of the reasons that I dislike that the game has made every class complicated. Several types of players, yours being one of them, were very suited to AD&D fighters and rogues due to the small amount of options available to them in combat.
There is a need for classes like that, but you will invariably get people who want to play that class, but be unhappy with the limitations and then come complaining that fighters can't have nice things.
However, my experience is that players who are best suited for a simple character are just as likely to pick a more complicated class. Just because they have problems deciding on actions in combat doesn't mean they don't want to have options. So the benefits of having a simple class in the game seems to be mostly theoretical.