I'm not one who speeds through, but that's also why I didn't work much on the recent 0.10 batches. I'm happy I likely provide more accurate data, but 10 images for 0.10 checking diligently for 3 values per image and not speeding leaves me with a poor hourly. Adjusting the image count down to 5 or upping the pay is a necessity. Also, I'm not a big fan of a new qual test for workers who have already done hundreds or thousands of HITs for you. I'd be up for existing workers being granted the new qual and then implement the tiered system and see how it goes. If you aren't getting the workflow you need on the batches at that point, then it seems like a good idea to open up a qual test for new workers. Also, I've had quals that adjust before and one of the main things that needs to happen if you go this route is that it needs to adjust both ways, not just deduct points. If you get something wrong it needs to deduct a point per whatever number of HITs you determine, and if you get something right it needs to add a point per whatever number. You can also just have someone needs to monitor cases that are falling near the disqualification line and reset the number if the overall work product is up to the standard you set. The latter has worked fine for me in the past as long as there's someone viewing and responding to messages when they are sent after workers notice they are getting too close to the disqualification number. Whatever approach you choose, I think being transparent about it is best.