I love the idea of doing up Hacking like Spellcasting. The mundane stuff can be put into other skills, this should be straight-up cyberwarfare and nanowizardry. Limiting by tech level is a bit of a problem, I'll admit, since there's no similar limit for magic. I think you could have several different "schools" of hacking and just bar as required. Surveillance gets you into cameras and bugs, cyberwar debuffs enemies, overclock buffs allies, drones replace summons, maybe an "omniprojector" school for more direct damage "programs". (Thinking along the lines of the tech attack abilities in the Mass Effect series here, like Incinerate, Overload or Cryo Blast.) So if you limit modern hacking to, say, Surveillance, you can keep it to plausible hacks of security cams and maybe aerial drone footage, whereas cyberwar would be more at home at the tech level of most early Cyberpunk (see also stuff like the recent Syndicate reboot) and omniprojector is just shy of singularity-level tech.