A great Article, my dear Patrick. Ultra Thin watches deserve more attention, indeed.
And there is even more " Ultra Thin " watches... This Master Ultra Thin Blue enamel, for example, is only 3, 60 mm high.
Here you have two challenges: Ultra Thin, of course, but also Skeleton.
My favorite are those made by Jaeger Lecoultre. The MUT 34, the MUT Jubilée 39 from 2013, in platinum, and the UT 39 Enamel, even if it is one millimeter higher, due to the enamel dial.
The MUT 39 Enamel White Gold:
You are right, the Master Ultra Thin watches are worked in the Grandes Complications Workshop at JLC. For the reasons you mentioned.
The Cal 849 is probably not the best finished, but it is very nicely decorated and offered at a price which is very fair. A very good quality / price ratio, and a very serious watch.
I will get one of them, one day. Now I need to make my mind between the MUT 34 and the MUT 39...