We would like to use a model to measure the customer risk based on user activities outside Risk Authentication and then feed a value to the user behaviour module in order to influence the risk score.
So we would like to know if it is possible to inject a value(s) into the model, if not, what can we do in-order to achieve this using RA?
User behavior model is now dependent on set of specific feature set, right now it is not possible to achieve this and it will require product change. I am in favor of this idea and will highly recommend that you open an Idea( Enhancement) on the communities side.
What is possible right now is that you can write a callout and get the Risk Evaluation done for the Non CA Risk server and then feed that data to CA Risk server. There is not much information available in the documentation so it has to be a services task if you want to take this route.