I can think of two solutions that could work from a simplistic approach.
The first would be to have a person atom that is only a dick and balls and have the ability to attach it to the female model.
The second is to have a way of just putting the male model inside the female model so that only the dick and balls are showing and hide the rest of the model, making it so the two objects can keep collision on, but do not collide with each other.
The challenge with these ideas is seams, but I'm sure some clever texture wizard could fix this especially if it was a few hired (by meshed) professional artists to make textures and models for VaM.