It sounds like you are aware of the negatives of weight of up high. For me, it is never worth the trade-offs. I don't think it is a good practice to encourage.... Hmm, just what size vehicle do I need to carry a 105 pound 20' Old Town Canoe XL Tripper? ...
I'll agree that avoiding carrying things on the roof is a good practice, but sometimes the roof is useful for other than keeping the rain/snow/sun/... out of a vehicle.
My "roof rack" on my 98 Jeep Wrangler TJ ran front brush guard to rear bumper. 1" tubing (.120 wall) and 3/4 #9 flat expanded metal mesh combined with a welding gun be quite useful.
I could carry 24' lengths of steel, canoes, lumber, and/or 4'x8' sheets of plywood. Yes, I was careful about how much weight I carried and how I drove, but that Jeep carried things in to places that large vehicles couldn't.
The rack sat high enough to be able to remove/install my hardtop and remove/install/use my softtop.
I also had a small tent I could set up on the expanded metal mesh. Camp in 6" of standing water? Sure, why not?
The hood could be lifted and supported the usual way.
The rack was removable without the need for a metal saw.
... Hmm, I even managed to include a few design thoughts. ...