Reverse Osmosis product water can be treated to make it suitable for copper piping. That will be one of the easier problems to solve.
There are those who believe home owners can't be trusted to operate a well with a cartridge filter. That is nothing compared to operating a reverse osmosis system if they are going to have more than an under-the-sink system for a bit of drinking and cooking water.
The first thing to be done is to determine what the water can be used for without treatment, and how much water must be treated. That requires a complete water analysis and discussion with the homeowner.
Then a tradeoff of the options must be done. The options should include hauling water, collecting rainwater (not much in Phoenix), different well (what do others get from wells), split systems to minimize the amount to be treated, extreme conservation, combinations of the above, and others that I haven't thought of. How much can the owner afford, and how much do they want to spend for convenience?
The tradeoffs must be based on concept designs for the alternatives. It will involve some expenditure to get to the correct decision.
The customer should take time to be fully informed about the options, because the customer will have to operate the system, unless you have a "cost is no object" customer.
This is the kind of situation where the customer would be well served to find a knowledgeable person that they trust who has no financial interest in the outcome of the tradeoffs and the final choice of system.
Here is a link to start. http://www.appliedmembranes.com/