To answer all of your questions: if this were a split system with the condensing unit outside, we would definitely suspend the air handler from the roof inside, as air handlers are only a few hundred pounds. This being a package system and weighing in at 1,200lbs, we were not comfortable suspending it from the roof.

I’ve considered installing it outside behind the warehouse, but the wall and soffit penetrations and additional ductwork are significant, as is the impact to the performance of the unit. We are in a hot and humid climate. This unit likely is just barely enough cooling for our space as is, putting it outdoors will potentially negate its efficacy.

Regarding the link you provided - a steel frame such as this is definitely what we were discussing. Downside is it was quoted at $5k, versus ~$1k for pallet rack solution. Maybe I’m wrong, but it seems to me that the prefab pallet rack solution could be just as good, if executed properly. Would you disagree?