Retired FAA, NATCA Member
Re: Left downwind vs. Left closed
You need to remember that "LEFT TRAFFIC" is the standard, so baring other instructions 99% of pilots (civil, commercial) will enter left traffic, except for those few who don't get it. I've seen controllers not issue "enter right downwind or right base to traffic" and have an arrival cross over the departure corridor and enter left traffic and almost create an ugly incident, which would had been the controllers fault.
As to telling a pilot where to enter the pattern, I always instruct them to enter the dowwind, base, or straight in (the way I was taught over 25 years ago).
Like ATC I'm working as a contractor at an army base in Afghanistan, let me tell you that foreign pilots don't have a clue about traffic patterns. Army pilots don't understand that being cleared for the option means you don't have to request takeoff clearance every single time when they are in the pattern, as well as a few other basic pattern terms.
I've been here over 5 months and still can't figure out why Army Helicopters fly patterns wider than a B52 pattern, I've been tempted to tell a few to "Please keep your pattern within the confines of Afghanistan", I've literally lost sight of a few because of their bizzare patterns.