This might be a case in which it would be useful to go to the provinces where they have dual charging, as they do in Ontario, and talk to them about how they're dealing with this problem. It may be that you have a charge and then it's dropped, because it's recognized as it proceeds through the judicial system that the person being charged was the victim, not the aggressor. There are ways for the police to note that in their initial charging.
In some cases when the police are on those calls, I think they feel their hands are tied and they have to.... You're there and you have two people who are very angry and upset, and both are making accusations about each other. It is possible, over time, to figure out that one person was clearly the aggressor and the other one was defending himself or herself. In the initial case, the police feel they have to charge both.
In talking to the jurisdictions where they practise this, there may be a way to figure out a way of wording the exclusion such that it doesn't unintentionally capture the victims of violence. That's beyond my expertise. You need to talk to the police forces about how they handle those cases and if there's some way to create a definition that would capture those people who are victims but who are still charged initially.
It's a sticky problem, and I don't have a perfect solution for it.