I like your idea. I read most of the Reddit thread, but i did not read through all of it, so i am not sure if someone else has made the same suggestions.
My idea of how the website might work is that builders would have there own page similar to etsy and they could decide whether to come up with builds and sell them as they see fit, or taking custom orders and building them to order, or some combination of both. Also, the builder would be responsible their own advertising. I think most problems with independent custom computer builders is that they have to rely on marketplaces like ebay which is getting expensive to sell on. If the serious builders could have there own pages they could advertise with social media, or on any website they want, but it would be on the builders to get costumers not the website. which i would think would create a competitive market without builders building for free because they would have to somehow promote their own page.
