There's no requirement that the Kickstarter complete the core project - just that they provide any promised reward.
Many projects, where the project is highly speculative, provide explicit rewards and then an offer to get the benefits of the main project that's conditional.
Also, in what way is it not like an experimental house design using, eg, 3d printed concrete (in some new manner)?
There's a well established body of contract law about how to handle that kind of contract to build a house with a new technology, and the liabilities involved.
Many projects, where the project is highly speculative, provide explicit rewards and then an offer to get the benefits of the main project that's conditional.
Also, in what way is it not like an experimental house design using, eg, 3d printed concrete (in some new manner)?
There's a well established body of contract law about how to handle that kind of contract to build a house with a new technology, and the liabilities involved.