Youe don't Need one but it does make things a bit easier. It makes it easier too to install additional electircal accessories later...like Gerbings, HyperLights, etc. Also you are not tapping into as much BMW wiring.
I installed a CenTech fuze block before installing the MotoLights. While you may be able to install the wiring without removing the fairings I think that you will be able to do a better and neater job if you do so. Removing the tupperware is not difficult but does take a little of time. I installed both fairing mount and caliper mount driving lights and tapped the parking light circuit to provide a switched power source for the relays.