I'm particularly drawn to this idea. Especially with it being a good source of energy. Could you possibly add a Thunderstone lightning rod of some sort? Many times as effective at gathering energy than your average steel/iron lightning rod, even more so if it's Refined.
I will probably update this thread on Monday... I'll be gone for the weekend so you guys will have to wait... Sorry, don't hit me!
Really like this idea! As an underwater based character how about this - If any thunderstone items used in water then all nearby creatures (including self) take damage. Thunderstone armor not wearable underwater etc..?
*Imagines wearing Thunderstone Armor, & jumping into a body of water, then watching a hell of a lotta Water Monsters get electrocuted to death while I gain 3-4 Levels in 2 seconds...*