The problem with separating loco and cab car is fundamental. Let's say X route comes with one loco and one cab-car. Would the cab car layer only activate if you have the BR101 leaving those who don't have it with half DLC? Include the BR101 so who bought the DLC wasted 15€? The only solution would be either to include another IC loco (such as the BR120) or using the MRCE 182 (or even the 146) for hauling the cab car and then let the 101 substitute it.