The payload is a small habitat, comparable in size to a the shuttles that NASA has sent up in the past. It should be expandable: some sort of fold-out pre-fab, or more likely just some inflatable bubbles, to provide additional living space. Power would be provided by solar paneling, of course. All of the equipment would be designed around two basic principles:
1) Given optimal conditions, it should be able to support life in a lunar environment indefinitely. These should be devices which, if they operated perfectly (never wearing out, 100% efficiency) would be able to convert human wastes and lunar minerals into enough food, air, and water. The theory for these kinds of tools exists, I believe (although they may require eating little but yeast for the first several weeks).
2) Given real-world conditions, the equipment doesn't need to last more than a few months. It'd be nice if it did last longer, but the usual layers of redundancy that NASA provides to ensure the lives of its astronauts should not be a priority. Instead, tools and materials should be provided for crude repair work, and the crew should be selected for creativity and adaptability.
The crew for this mission should be highly intelligent and highly trained, like all NASA crews, but they should know going into this that they are expendable. They are not expected to come home. They will not be rescued. They are not expected to survive more than six months. Nonetheless, they should do everything in their power to survive as long as possible.
The crew should be small, probably 2-4 people. Married couples who have proven their ability to live and work together for an extended period under difficult conditions would be a logical choice. Expertise should be distributed: at least two members of the crew should be medically trained, for example, to reduce the chance that a single death or incapacitation will leave the team utterly crippled.
The one system that should have multiple redundancy is the communications link with Earth. This is partly for the benefit of the crew (they will likely be relying heavily on it both for entertainment and for technical support). But it is primarily because this is the entire point of the mission: to gather information about what ways in which a real attempt at a lunar habitat would fail. This is a trial run. It is a beta test.
From the moment the craft leaves the ground, designers are to begin collecting information about what needs to be improved. What is too fragile and needs to be hardened? What is too complicated and needs to be simplified? What is too inefficient and needs to be streamlined? What, on the other hand, works just fine? This is the groundwork for the design of the second mission
The second mission will be similar to the first. It should attempt to land near the original habitat, and it should be designed so that it can be moved across the lunar surface, perhaps via a large dolly-like platform (this should be much easier than moving it on Earth, as the gravity is substantially less). It also needs to be able to be linked via airlocks to the first habitat, likely by some sort of corridor tubing. Thus, the second crew will have double the living space that the first did.
The second mission's equipment will include improved versions of the machines that failed in the first mission. It will not have improved versions of things that worked just fine originally: these do not need to be fixed. It will also have parts to repair machines that failed due only to some small detail, but were otherwise sound.
Like the first mission, the second will also not carry extended redundancy. It doesn't need to. The still-functioning devices from the first will provide that, and the broken machinery will provide spare parts.
This crew might be slightly larger, perhaps 4-6 people. They will be expected to survive longer than the first group, perhaps even an entire year. They might make it until the next mission takes place, but this is not to be expected. They are also not expected to return: this is the second beta test. If they live for six months, then this mission is also a success.
The third crew will be much larger, at least a dozen people. Probably more. Their equipment should be much broader in focus than that of the previous two: simply surviving for a few months to a year should be assumed; this mission should be planning for the long term. If there is still uncertainty as to how to make something work, then two, three different models should be sent. Redundancy is no longer a bad thing. This mission will be, by far, the most expensive of the three. It is not a trial run. It is the real thing.
The third crew should also not expect to return home. But they should plan to be there to welcome the next wave of arrivals.
I am sure this plan has flaws. Aside from the political difficulty of planning a suicide exploratory mission, what are they? You tell me.