Itll be fine but you rad fans are pulling air into the case. If you've got other intakes I'd flip them to exhaust.
I think you're right to be concerned. Is it possible to mount the fans for the rad to the outside of the case?
Yes, once the rear panel is removed you would still need to apply some major dremel modification to generate any significant airflow. It's an oddly designed case considering the options they could have had for airflow - i think looks over practical use was the driving force of the design - no matter how many grommets they put in.Isn't the rear panel of the Raven 01 mainly solid with only some small ventilation holes at the top?
That bottom fan will just be sucking the hot air back in that your psu dumped underneath.
Just looked at the pics. That's a terrible case for watercooling!
Doesn't really matter how you put the fans they're just going to be circulating warm air.
If temps are fine do whatever works. But as above, either go air cooling or choose a better case if temps are an issue.