If you want clean, simple, and expandable, the MotoGadget m-unit and m-button can not be beat.
Here's my headlight with the m-button (all handlebar controls connect to it) and the m-unit under my seat (control wires in on left, supply out on right side). Only a single 30a fuse from Reg/Rec to battery, no relays, no diodes, no bullet connectors.