I think it would be a really thematic thing for them to do, but for as much as they pay lip service to "magic and technology don't mix", in practice it's more like "magic trumps technology", because the antidote to magic is not tech, it's more magic. That's the bed they've made and we get to lay in it.
I think if you do this, take a light touch. The game is balanced around the current state. I like your Edge granting idea against mana spells. And perhaps reserve it for truly low essence characters, like sub 1 or sub 2.
For other mundane defenses against magic, look into Mystic Weave mod for armor. It's expensive, but starting characters can get it.
Also look into mundane-friendly enchanted items in Street Wyrd.
Hopefully the augment book, Body Shop, has implant versions of Mystic Weave .