Jennifer Hale has a nice, distinct voice. It wouldn't feel right to me.
Well I wouldn't remake it. But yeah I would keep the same voices if it was remade. Anyone else voicing Garrus, Wrex or Tali wouldn't feel right and Jennifer Hale is one of a kind, imagine some else not Keith David voicing Anderson. Shephard might even be her best voice role as well.
I'd trust that more than them making a new Mass Effect game.