I agree with your concerns about economic sustainability and the need to make sustainable food economically just for all, the producer as well as the consumer. I share your idea that landowners could probably be persuaded to “lease” (for free) use of their land for a CSA in exchange for a share. Where I live, if someone makes $1,000 a year on their farm land, they get a huge property tax break. For that reason alone small landowners like me would be willing to let a new farmer use a piece of their land for a CSA, for free. The farmer would have to build some fencing, but would provide water (we have a large pond), manure (horses graze in my pasture), all the leaves you could want for mulch or composting, and the land.
I’ve been talking to folks near where I live in North Carolina and I think it’s doable. Which means it should be doable anywhere where the landowner gets some kind of tax break or incentive to put some of his/her land into farming.
Keep working on it, great idea and one that has to be addressed if we are every going to have truly sustainable farming.
Dee

Another thing is to organize with Habitat for Humanity to encourage the inclusion of vegetable garden space with every home they build. This is being done in at least one location. When we build space for gardening into homes, we can motivate people to use the space or at least share it with neighbors who do want to garden.