I agree with the useless 'realistic representations' of air handlers, RTU's, etc.
It is much better to have an Oblique Angle cut-way view with semi realistic equipment such as dampers, fans etc.
Another thing that is a useless between jobs in a perspective view that changes size from left to right. Can use this graphic on a second project if the equipment is slightly different.
All of my air side equipment graphics are Oblique so anyone that knows how to use Microsoft paint or other simple graphics programs can cut and paste from one project to another.