I think we have one in the office.
Can you cite the exception to this rule? EVERY residential roof top unit in AZ (and I am assuming elsewhere) has sleeved NM. Have all the inspectors overlooked this........ forever?
NM HAS to be allowed in exterior sleeves. I have done it thousands of times and have had it inspected countless times. Somebody somewhere would have caught it. When doing service changes or adding circuits the NM is generally sleeved. They don't consider it "conduit" if it is a sleeve.
Bender. Get a "hub" to fit the top of the panel. It has threads to accept your conduit connector. Make it plumb and strap it appropriately. To ME, PVC looks like homeowner work but apparently it is done a lot. I would use EMT to make it really clean. The PVC tends to warp and bow.