Anybody out there know how one would safely/securely install a third row of seats?

Not a chance. This SUV is WAY too small for that. The floor would have to be dropped a good 8-10 inches to make it doable.

Plus, how would someone get to the third row seats without climbing over the back seats? Seems like too much effort for too little return.

Yes this is a crazy question. No way this is possible without major modifications to the rear of the vehicle. Buy a Commander if you want 3rd row.

Bolt the seat to the roof. Or purhaps buy a bus.

Then there's the safety issues associated with aftermarket seats - how well are the installed and bolted to the frame (will they break loose in crash and injure 2nd row passengers and those in the 3rd row seats?)? will they provide proper safety if rear ended? where will the seat belts attach and anchor to?