Hi R.Og,
so, in the basic 21" iMac there is not the connector for the blade SSD drive, just the traces.
I may presume that the high end 21" has the connector (with or without fusion).
Anyhow, even if there is no reason Apple does not provide it, I've not yet seen any teardown of the higher 21" iMac without fusion, so we cannot be definitely 100% sure the connector is there, as shown in your base 27" teardown.
My question:
Is the connector in the 27" iMac soldered to the board or can we dream and it is pluggable in some way?
Here in Italy the base 2012 iMac is 223 euros (not 100$) more than 2011 iMac and I do not want to pay 1829 (about 2420$...) just for the luxury of having a fusion drive