Just a couple ideas I thought I'd mention:
What about adding a line to the section about familiar death saying that a witch will generally aid another witch who has recently lost a familiar and will teach the familiar spells to help replace those that were lost? It would provide the character some opportunity to replace spells. Granted that would require there to be a witch in the area.
A second possibility that I heard someone mention was to give the witch an X/day ability where, as an immediate action, the familiar can be teleported away from danger.