All that said, there isn't anything game breaking if you let a player be both. If you're using anything like the normal character generation methods they'll be terri-bad at both though.
The other suggestion is be a Herimetic Mage with some trodes and a Deck. It's a tight build, one of the few that benefit from Skills A IMO. But Magic 6, few spells, spirits, *meh* hacking pools, crappy but good 'nuff Deck. Go Ravenclaw! Suffers from not enough Edge. And you have to be a Human. And you're a virtual cripple compared to normal runners. But Brains!!! you got em.
All depends on the player's motivation. If the motivation is Spellcasting Hacker, easy-peasy. If the goal is a snowflake Mage&Technomancer combo, then you'll have to house rule something.