Some good points. I do think it is important that the instructors in the industry present as near a unified view as possible on this point because, although 'learned discussion' has its place, it confuses the hell out of the students if they think that even the instructors do not agree whether a great circle is a straight line or not.
Whilst I take your point that some people may have an 'intuitive vision' that rhumb lines are straight lines this does not stand up to inspection and should be countered early on in the training.
Certainly a straight line on a map is not a rhumb line (except on Mercators), it is a very close approximation to a great circle. Sure, we draw a line on a map to fly from A to B but if it has any length at all we can see that track direction at the beginning is not the same as the end. Yes, this might be partly due to changes in variation if you are measuring magnetic tracks but, if you measure true tracks against the meridians you can see the effect of convergency. In light aircraft you might measure the start track as, say, 060, and the end track as 062 and choose to fly 061. In doing this you are actually flying the rhumb line (half the convergency added to the initial GC track) but drawing the great circle on the map. The track displacement is so small you don't notice it in flight, even if you can hold heading to 1° of accuracy.
For me the clearest indication as to which is 'straight' comes when you look at the globe. Yes it is possible to choose a viewing angle where a rhumb line looks straight. Look at this image, at the latitude that passes through southern France.
The proper way to look at it, though, has to be from directly above, where the rhumb line can be seen to be curved just like it is on
all map representations (except Mercators). If you look at great circles from directly above they always look straight just like (their very near approximations) do (within the usable areas) on
all charts (except Mercators)
Consistency alone calls for rhumb lines to be sketched as curves, anything else confuses.