Lots of firms do something similar to this. However, it would be feasible to not go too far down for a number of reasons:
1) If the volume of certifications is large, it might get fairly cumbersome to administer, especially if weighed against benefits
2) Going down too far may be getting you certifications that aren't really linked to any key controls--so therefore may be somewhat irrelevant
3) SOX should be controls over financial reporting, although a lot of the documented controls tend to not be directly linked--if you go too far down the ladder you might start getting certifications from personnel who really truly don't comprehend what they're certifying for--not to say these people are incompetent, but just don't tend to ever have to view their job within the big picture (in this vein, we have managers in key areas to certify, but don't go below that. These managers are supposed to be the link between line personnel and the bigger picture and are therefore intrinsically responsible for the function of their direct reports anyway)
Just some thoughts.