mmh, so m_transform is possibly illegal for quite some time? imo it should be only illegal at one point: just after the step resulting in a collision was performed and then it is immediatly reset to a legal value again. 
We have to discuss this further probably, but imo it's not the objects that move themselves. They are moved by higher entity that makes sure everything is valid all the time. As soon as we give objects the ability to move themselves satan's kitchen isn't far.