How you like them apples?
For as long as people have whined about DE-zapping I've thought about this idea, but never passed it on. Now is the time :)
If a Hidden Tesla is within radius a lightning spell it could pop-up and divert the lightning so the effective damage that the lightning spell does to the target area as reduced by 75 % (for example). Hence the Hidden Tesla would function as a lightning rod protecting the target building or area from lightning.
If SC would implement such a feature one could actually do something against DE-zapping :)