I'm a firm believer in the "1 man (or woman), 1 Kit" philosophy, but maybe thats just my military backround. People in general should take responsibility for their actions, if your tank falls off when you jump in, it's pretty much your own fault no matter who set it up. As a certified Diver from any agency, you are expected to be able to setup your equipment and/or inspect it (with buddy) if someone else has done it for you.
That being said... I have noticed on the few trips I have been on that there are a lot of ppl out there that hop on a boat without any clue as to what they are doing. IMO, trained boat staff should be ready to assist these individuals by walking them through the process, using a hands-on approach only when absolutely required.
One last piece of wisdom I have been taught: "Never pass a fault". If you see someone doing something completely A** backwards, either get the attention of the staff or help that person out. Who knows, you might have just saved that persons life.
As far as the original post goes, I think there are only 2 options: Do not offer setup or have only trained staff setup the equipment, plain and simple.