Contemplating the idea of using two conductive ribbons as the electrodes. Arc location will be randomish given perfect conditions. Place a small conductor between ribbons where you want more frequent discharges (dielectric grease spot?) Other ideas on randomization of arc strikes?
There are conductive foils that would work. Also decorative ribbons that include a wire, and electric fencing tape that also includes conductive wire. Is there a material that can be made more or less conductive on demand?