blackoper: I think it is a somewhat simple idea, but as with a lot of stuff the devil is in the details. My design mounts the fan, linkage and driver on a shaft supported on both ends with angular bearings. The shaft goes through the vent in the driver. Then I plan to use a 3 phase motor and speed control to turn it. One issue I am having is that if you leave the driver whole, you have a large cone (mine was 15") in the way of your airflow. The Thigpen is only 17" in diameter, so that doesn't leave you with much! If you cut out the cone, then the coil is only supported by one spider and the bushing of the linkage. You have to mount the driver in nearly perfect alignment otherwise the coil will rub on the magnet. There is very little clearance. In addition, the driver has this rather strong magnet that wants to pull it to the shaft which will basically crush the coil instantly. There are ways to mount everything in a order that would work, I think.
Also note that going "beefy" and with metal blades you will need a strong driver and you will need to calculate the max frequency it will do based on the additional mass you are adding to the "cone". I need to get to ~25 hz because I am using a folded horn above that.
I don't know if any pictures are left on either thread, but I can edit the links to them if you ask. (They are a pain to fix.) The new version of AVS broke all my pic links.