Umm, what's the point in that?
Since SATA has nearly all the same features that SAS has these days?
SATA reminds me a lot of USB... A device can be USB 2.0 compliant and only support 1Mbit/sec transfer rate... Similarly, you can call something SATA II, but it may not support any of the optional features of SATA - NCQ, Port Multiplier, Staggered Spin Up, Port Selector, External SATA, Hot Plug...
As far as I know you'll never see a SAS drive/controller that doesn't support these features. Of course, as you already realize, you can simply ensure that your SATA controller and drives support the features you need, but this may limit you to only a few options that have been qualified to work together.
The other advantage, that is not available in SATA, is the physical connector. SAS drives have 2 data channels on the connector, SATA drives only have one. This second channel can provide redundancy in case of drive/controller/cable failure or load balancing between controllers.