you still forget about the Dovin Basels and thier mini balck holes.
Also the exterior of all Vong craft is CORAL which is the next best thing to a Rock. Rocks do not conduct electricity very well.
And yes a Ion would work on a living creature (Mara Jade got hit by one) in Heir to the Empire Trilogy.
But would ions be enuf? you would have to get past the Dovin Basels, and the coral Coral first.