To be honest B412, UMs are being treated just the same as they were back in 2006 despite the cost cutting that is currently taking place. And that is that they are being treated well. Two years on and re-reading your post there still seems to be a question mark over the form of booking that you made. Regardless of whether the passenger is a UM or not I do not understand why they would not rebook the customer onto the next available flight after a missed connection unless of course that 16hour wait was the next available. Also, as for sleeping on a camper bed in the floor, well adults perhaps would have been offered a hotel but when it comes to UM I would imagine it would be very difficult to find an airline employee willing to babysit a UM in a hotel room in this day and age of random accusations! Sounds like they made do the best they can!
I personally would never book a UM via somewhere but if I did I would make sure it was with the same carrier. So for example if I needed to get someone from IAH to Lagos I would book with BA or KLM all the way so that the UM does not become a football being kicked from one agency/airline to another! Booking a UM via somewhere on airline A with a connection onto airline B via agency C and D is only going to create problems. Also with UM's, as they are generally held back during disembarkation etc it is best to ensure that their have sufficient time to make a connection, I personally would say minimum three hours in airports such as ORD or LHR!
You need to appreciate that perhaps your particular incident was unique and a product of a catalogue of errors that took place from the moment you made the booking instead of making a sweeping generalisation about treatment of UM's industry wide!