Hmm. You'd need all the fans to be 4 pin. The splitter draws power directly from the psu. Only the pwm signal itself comes from the mobo.
As far as driving every single fan, you'd need to customize the harness to work. Depending on what came with the fans, you may have some parts to modify. By that I mean molex daisy chains, etc...
Anyways, this would provide your entire cooling system to be controlled from your cpu fan header.
An even simpler method would be to hardwire all or most of your case fans to 7 volts by making a molex adaptor. If you've got that many fans, I've got a feeling that you won't have to spin them too fast in order to get results.
For example, I have 2 front intake, 1 side intake, 2 top exhaust, and 1 rear exhaust. I run them all hardwired at 7 volts. I have a 3770k cooled by an NH-D14 (which is also uncontrolled) and a Gigabyte GTX 670 (which spits it's heat out into the case) and my temps are very low. Another benefit is that the case is quite quiet. The difference in running all of my case fans at 12v and 7v made for only couple of degrees. We're talking 2-3c during gaming sessions.
If you don't mind a little soldering, you can try the 7 volt trick and see what results you get. If that isn't up your alley, I doubt modifying the pwm splitter would be either. Hence, you're back to looking at standalone fan controllers. Sadly, I can't really help you there.