A powered element which lets particles pass through it wouldn't work very well. The game can only store one particle per pixel in the pmap (which is used to find nearby particles to switch on/off or interact or collide with). Switching on/off would only work properly if putting pixel thick e-wall in the pmap was prioritised, but it would then always act like INVS sometimes does (collisions are broken, allows an infinite number of particles to be in the same place).