Ecradda:
Custom is a very expensive word
one off pieces tend to raise the cost of something that you would think should be 10 bucks to upwards of 100 bucks. Not saying this is the case here but I have done custom work before and had it done for me, overall it doesnt justify the price.
To the best of my knowledge the curent control board is set up to handle only one fan per board, by changing a few components it may be able to handle 2 maybe 3 but not sure on that.
The good news is since all the boards run off 12 volt circiutry you can add more boards to control more fans, I dont see this as a big problem since most PSU's and MB's support several fans