Remember, anger and rage are just feelings, they are not, in and of themselves, bad. If you feel anger or rage there are undoubtedly very good reasons for that. Size and experience differential between client and therapist are serious concerns, but ones that can be strategically equalized. I have done a number of consults with people who have similar concerns that they'll hurt their therapist if they connect with their anger, all of whom have been successful in finding ways to deal with their particular problems. As I said before, the room matters.
Some survivors do have alter selves who have been trained to fight in a more conscious manner.
If you can't speak to them directly, so that they can plan to manage their own anger, it will be important to set up sessions to defuse their anger and get it under control, rather than risk an unexpected outburst. A good solution is that of employing an adjunct person to be present for this initial anger work. I have found that most areas have dojos or other martial arts centers where trained people can be found. Martial arts teachers are accustomed to the abuses which frequently send people in search of defensive skills. Although they might not always be familiar with multiplicity, the dynamics of consciousness shifting is very familiar to them.