I really think this idea would work pretty well. As a scrambler, you have an awful lot of tasks to juggle, and it can be difficult to remember to give each cube a thorough check. However, a person with a set job of checking scrambles would not have nearly as much of a difficult time remembering to check cubes.How about having a person that sits at the scramble table and only checks if the scrambles are correct. That person could then cycle the puzzles that are misscrambled directly back to the scramblers.
Downsides are the need for a larger scrambling table, having more staff, and that it makes the scrambling process slower. Also, it still wouldn't necessarily be 100% effective. And probably some other stuff that I haven't thought of.
In any case it seems like a better idea to me than some sort of scramble checking cube cover.