This is a cool idea in theory, but it's just not practical. I want the Enterprise to be more than just a glorified delivery vehicle for colonies on the Moon and Mars. Colonies like that would be cool and all, but I can't imagine what possible benefits that we would obtain from them at this point in our technological development that could possibly justify the massive costs involved. After all, it's not just the construction cost, you also have to keep all of these facilities maintained and supplied. It would become a massive financial drain for very little return.
Now, if we ever can identify a planet around a nearby star that is actually capable of supporting human life, then I think proposals like this will be more realistic. If we are going to build the Enterprise, then I want it to have someplace to go - someplace to explore. Not just hauling supplies to Mars.