I like magic as powers. It just feels so straightforward and easy to balance (or at least to keep track of). You have the magic that you have, not some crazy spell list. If you need additional powers, you have rules for stunts. Yet I've never really been happy with just listing allies. So here is a set of powers that lets a necromancer control undead, create undead, and build up massive armies with soft limits rather than hard ones, and without too much hand-waving.
The powers given here are using multiplicative modifiers, which I recommend doing any time you use a powers system.