Godfrey,
it seems you have different definition of drawing or look at something different. By drawing I rather not mean AA or pixel detail, but overall look of the picture made with fast Leica lens wide open. Fast, as someone said that at f/5.6 all lenses look the same. No character at such apertures, allowing to differentiate them from eachother.
So, to come back to the sensor. Using NEX or RICOH or maybe soon Fuji - is not simply able to get me that 3D, that I see in for example in 35mm Summilux on FF wide open. It simply cuts off edges drawing. And these drawing is mostly visible when wide open.
If you attach 35mm Lux to APS-C sensor - you get picture as taken with ~50mm at f/2 on FF - what again - differs from what you get with 50mm Lux on FF.
Even if you attach big and heavy 24mm Lux - you will get picture as taken with 35mm Summicron, not Lux.
If a person makes most photos closed down, then there is no such difference in results, in fact latest APS-C may bring better pixel quality than older generation FF, especially if it is without AA filter.