I do not know the details of the implementation in the exponential churn model. But by looking in the classes, I think the calculation of the churn model uses the churn factor only as one component, but uses also other ones. In the calculateTransientCf() method of the ExponentialChurnModel class you find the calculation. And it expects a churn factor less than 0.5.
For your churn feature, I have to correct my previous post. It is already possible to enable churn only for some groups by using “<Properties enableChurn=”false” />” in the host builder configuration. But the time for activating churn is the same for all groups. If you also want this independet for all groups, you have to modify the code, otherwise not.
If this is the case i would introduce a new ChurnGenerator (look at the DefaultChurnGenerator) which has also some actions (which can be configured in an action file) to have this dynamic behaviour.
Hope you got the point 😉