I think the best solution would be to have a database of 3D models for cases & coolers. Maybe a site like PcPartPicker.com could do something like that, but they'd need cooperation from manufacturers or maybe some enthusiastic users to supply the models.
The models needn't be very detailed. At minimum, you'd need the dimensions of the main cavity and mounting position of the motherboard. I don't even know if motherboard standards dictate the CPU location. If not, then you'd need that too.
The benefit would be that you could see how much space there'd be for airflow, and maybe the site could even offer crude airflow simulations if the speeds of the fans are known.