It was offered by the dealership but at a much higher price. So presumably the roof can accept the weight.What is the make and model ,year of the OP unit?
An average Air con for a caravan is circa 33kgs. A hell of a lot more than an Omnivent.
Can the roof structure take the additional weight?
We never felt the need for aircon even when down in southern. France. The Omnivent in our Bailey was particularly useful and well used.