Love the idea of paying people. That's great. However, consider the perspective of someone who already has a job in the industry. If every company did this, I wouldn't be able to interview at more than one per week. Not only that, but the Friday and Monday onsites mean I miss work on TWO separate days. This would be a non-starter for me if I had any decent pool of interest from other companies, although it's great for people trying to break into the industry.
Another problem, depending on your philosophy. Specifying the exact technologies someone has to use means that you've closed yourself off to generalists, unless they have time to learn a whole new stack that weekend. Not that it's rocket science to do so, but that turns a two hour project for me in say Angular into an eight hour project in your favored stack. I can always learn your stack on the job, as any good engineer can.