I think the idea is an okay one and similar to how Melissa Balin sold her finished film.
But a new sales channel does not mean you can forget all your good sales practise. Where is the statement of quality? What has this writer done before? Who has read it and will give it a stamp of approval? Without that it may as well be blank sheets of paper. It might be a great script. But if it demands a high price then give me a reason to bid.
I think it is far too easy to misunderstand the concept of the new ways of selling and distributing. As we find more and more ways around the gatekeepers and approach the goal of connecting with the audience directly everything can appear easier. It appears to be easier to sell your script. It seems easier to distribute your film directly. In fact it is harder. The competition is greater and you need to work even harder to capture people's attention. But get it right and the pay off is massive.
With no agent fees and no overheads this writer could cash in. But to do that they need to become a better self-agent first. And that includes both promoting the work AND making sure it is ready to sell.