2G Charging Issues?

Ok, So I have been doing some thinking lately because I will soon be in the process of purchasing a new-to-me truck and would really like a professional looking iPod install. I know the 2G iPod Touches, new Nanos, and iPhones no longer charge over firewire, but have now moved to USB. My question here is this... I am just now starting to see these. My thoughts are that little thing cannot do more than switch the wire from the firewire dock pin to the USB dock pin, maybe a resister to cut down the voltage. My question here, couldn't this be a very easy DIY project for those who are interested? I feel that I could get something like this, hack it up, change the firewire pin and the usb pin, resolder, and walla... a charger that will now charge my 2G Touch?

Thoughts, or has anyone seen this mod tried yet? I may have to be the first to try it when I get the new truck.