John,
Thanks again for the air movement details. I just did some measuring and it would be possible to build a cabinet above the counter top. Sink access will be somewhat limited as the bottom of the cabinet would be above the sink. That sink gets used mainly for teeth brushing and shaving so usage would be possible but a guy 6'2" like myself will have to watch the overhead clearance. That's a small price to pay for air conditioning, IMO.
I will have to check measurements of these small A/C units to see what the cabinet size would be but I'm getting a good feeling about using some cabinetry to get the A/C mostly inside the plane of the rear exterior wall. If I locate the unit in the top "bend" of the wall and can bring some of my metal work skills to bear, this may end up reminiscent of some older round-top buses I recall. In that case, the guts of the A/C were covered with a metal housing so just the back panel of the A/C was visible to the exterior. It was quite presentable, surely better than having the raw A/C housing exposed on three sides.
Depending on the positioning of vents and controls on the front of these small units, I may be able to cheat out a few inches by locating the unit nearly up to the roof level. That would mean cutting the front plastic grill in most cases. I'll know more after selecting the actual unit.
Keep the ideas coming folks. Sometimes my original designs get discovered to be less than optimal.