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?

*edit 2017/04/27*

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?