Well, a modern litch might not be an animate skeleton. He might opt to transfer his conciousness into an undying robot form instead! There might not even be a reason for him to be a spellcaster if he can manage to master the requisite technology, after all sufficently advanced technology is indistinguishable from magic.
But, you asked for a Modern litch, and not a Future one. Saddly, I have neither. I just do concepts.