I wholly agree with your second statement. The space exploration industry has incredible barriers to entry. Without NASA or government funding or government agencies to sell to, there would be no SpaceX, no Blue Origin, no Sierra Nevada, or any other New Space company. Old Space, like Lockheed and Boeing, would still exist, however the Orion capsule and all of their space efforts would be nowhere near as large and advanced as they are now and would revolve entirely around surveillance, military, and scientific research/purpose only.

The SLS is receiving a lot of funding and has some strong congressional supporters. It all depends upon if the SLS starts going over budget and falling behind schedule. I think that that scenario is likely. Combine that with a successful Falcon Heavy launch and there will be considerable pressure to cancel the SLS. I would actually support that and go with the model that you describe.

Many people in the space blogosphere argue that space development should be 100% commercial and to have nothing to do with receiving government funding. E.g. SpaceX is just another form of space pork. I would disagree. There are certain situations where commercial firms need help getting over the initial development and operations barrier after which they can provide a more cost-effective service to both NASA as well as the market. Developing lunar ice is one of those things IMO.